What is the author’s main point in the last paragraph?Carbon-based chemistry is a significant indication of the possibility of extra-terrestrial life.We should exercise caution when speculating about the properties of extra-terrestrial life.Extra-terrestrial life may not necessarily be carbon based.We should not focus only on carbon-based chemistry when searching for life among the stars

It’s a question as common as brown dogs: will alien life be carbon-based? I’m asked this frequently, although I’m not sure why the public is so hung up on the elemental basis of extraterrestrial life. Probably, the fascination with vital soot is just a consequence of carbon’s high profile on Star Trek. The plot of this popular TV series gets viscous whenever the Enterprise detects ‘carbon-based life forms’ on some God-forsaken planet deep in the Galaxy’s nether regions. Hype aside,. . . there’s good reason why this element is the basis for life on Earth, and probably on most other worlds that shelter biology.If you remember your high school chemistry, you’ll recall that carbon has half of its outer electron shell filled. And because carbon’s outer shell is both half-filled and half empty, it can handily hook up with other carbon atoms, creating the sort of elaborate molecular chains and rings that fuel companies love to pump. Carbon, in other words, is adept at making complex structures. And complex structures are the bricks of life.Are there other contenders? Is carbon really so special, or did it just get lucky here on Earth? If you have a periodic table handy, you’ll note that the element situated under carbon is silicon, which also has four electrons in its outer shell. Ergo, silicon might also seem to be an obvious basis for life, a point that was first made at the end of the nineteenth century by the German astrophysicist, Julius Scheiner. The optimistic Scheiner was certain that other planets in our solar system (including roasty toasty Mercury) sported life.But his sunny attitude was misplaced when it comes to silicon-based beings. Silicon may be carbon’s chemical cousin, but it’s a poor relation. Because the silicon atom is larger, its bonds with other elements are weaker. While carbon hooks up with two oxygen atoms to make carbon dioxide, a nice waste product for both humans and SUV’s, the silicon equivalent, silicon dioxide, quickly assembles itself into a crystalline lattice. It’s better known as sand, and would make exhaling a gritty experience. The weaker bonds of silicon also preclude the easy formation of those long, same-atom molecular chains that underlie many biological compounds.If that’s not enough to dissuade you from silicon, consider this: there’s just a lot more carbon around. Cooked up in the searing interiors of stars, the cosmic abundance of carbon is more than ten times that of silicon. And by the way, if silicon is a distant second in the biology sweepstakes, the elements under it in the periodic table – germanium, tin and lead – are worse. They’re less abundant, and less inclined to make biologically interesting compounds.Of course, one must always beware of hubris in speculating on the properties of extraterrestrial life. Earth is just one planet among many billions in our galaxy. But when the Enterprise boldly goes in search of life among the stars, there’s good reason its scanners perk up at any sign of carbon-based chemistry.The central idea of the passage is:

Read the given text and answer the questions that follow:Life on MarsA new study published in the journal Science shows definitive evidence of organic matter on the surface of Mars. The data was collected by NASA’s nuclear-powered rover ‘Curiosity’. Itconfirms earlier findings that the Red Planet once contained carbon-based compounds. Thesecompounds – also called organic molecules – are essential ingredients for life as scientistsunderstand it.The organic molecules were found in Mars’s Gale Crater, a large area that may have been awatery lake over three billion years ago. The rover encountered traces of the molecule in rocks extracted from the area. The rocks also contain sulphur, which scientists speculate helpedpreserve the organics even when the rocks were exposed to the harsh radiation on the surface of the planet.Scientists are quick to state that the presence of these organic molecules is not sufficientevidence for ancient life on Mars, as the molecules could have been formed by non-livingprocesses. But it’s still one of the most astonishing discoveries, which could lead to futurerevelations. Especially when one considers the other startling find that Curiosity uncoveredaround five years ago.The rover analyses the air around it periodically, and in 2014 it found the air contained another of the most basic organic molecules and a key ingredient of natural gas: methane. One of the characteristics of methane is that it only survives a few hundred years. This means that something, somewhere on Mars, is replenishing the supply. According to NASA, Mars emits thousands of tons of methane at a time. The level of methane rises and falls at seasonalintervals in the year, almost as if the planet is breathing it.NASA suspects the methane comes from deep under the surface of the planet. The variationsin temperature on the surface of Mars cause the molecule to flow upwards at higher or lowerlevels. For example, in the Martian winter the gas could get trapped in underground icy crystals. These crystals, called clathrates, melt in the summer and release the gas. However, the source of the methane is still a complete mystery.The world of astrobiology considers both of these studies as historical milestones. According to this information, Mars is not a dead planet. On the contrary, it is quite active and may bechanging and becoming more habitable.Of course, this means further research is necessary. Scientists say they need to send newequipment to Mars, equipment that can measure the air and soil with more precision. There are already missions underway. The European Space Agency’s ExoMars ship lands in 2020 and will be able to drill into the ground on Mars to analyse what it finds. Additionally, NASA is sending another Mars rover in the same year to collect samples of Martian soil and return them to Earth.The possibility of life on Mars has fascinated humans for generations. It has been the subject of endless science-fiction novels and films. Are we alone in the universe or have there been other life forms within our Solar System? If the current missions to the Red Planet continue, it looks as if we may discover the answer very soon.Your answer1.Mars has fascinated humans for generations. State which one of the  facts given below hold INCORRECT, to support the above statement*1 pointa. Presence of the essential life components like organic compound.b. Water sample collected by the scientific vehicle contained very small elements of an organic molecule.c. Presence of life supportive natural molecules like Methane.d. Mars can be said to have seasonal variation

What characteristics of carbon (C) makes it essential to living organisms?

Comprehension (Question 03) Directions: Read the passage and answer the following questions. The atmosphere forms a gaseous, protective envelope around Earth. It protects the planet from the cold of space, from harmful ultraviolet light, and from all but the largest meteors. After traveling over 93 million miles, solar energy strikes the atmosphere and Earth’s surface, warming the planet and creating what is known as the biosphere, the region of Earth capable of sustaining life. Solar radiation in combination with the planet’s rotation causes the atmosphere to circulate. Atmospheric circulation is one important reason that life on Earth can exist at higher latitudes because equatorial heat is transported poleward, moderating the climate. The equatorial region is the warmest part of the earth because it receives the most direct and, therefore, strongest solar radiation. The plane in which the earth revolves around the sun is called the ecliptic. Earth’s axis is inclined 23.5° with respect to the ecliptic. This inclined axis is responsible for our changing seasons because, as seen from the earth, the sun oscillates back and forth across the equator in an annual cycle. On or about June 21 each year, the sun reaches the Tropic of Cancer, 23.5° north latitude. This is the northernmost point where the sun can be directly overhead. On or about December 21 of each year, the sun reaches the Tropic of Capricorn, 23.5° south latitude. This is the southernmost point at which the sun can be directly overhead. The polar regions are the coldest parts of the earth because they receive the least direct and, therefore, the weakest solar radiation. Here solar radiation strikes at a very oblique angle and thus spreads the same amount of energy over a greater area than in the equatorial regions. A static envelope of air surrounding the earth would produce an extremely hot, uninhabitable equatorial region, while the polar regions would remain inhospitably cold. The transport of water vapor in the atmosphere is an important mechanism by which heat energy is redistributed poleward. When water evaporates into the air and becomes water vapor, it absorbs energy. At the equator, air saturated with water vapor rises high into the atmosphere where winds aloft carry it poleward. As this moist air approaches the polar regions, it cools and sinks back to earth. At some point, the water vapor condenses out of the air as rain or snow, releasing energy in the process. The now-dry polar air flows back toward the equator to repeat the convection cycle. In this way, heat energy absorbed at the equator is deposited at the poles and the temperature gradient between these regions is reduced. The circulation of the atmosphere and the weather it generates is but one example of the many complex, interdependent events of nature. The web of life depends on the proper functioning of these natural mechanisms for its continued existence. Global warming, the hole in the atmosphere’s ozone l

Recall how carbon gets from the atmosphere into living things.