17. The “lead” inside the common pencil is actually not lead at all.a. Lead is commonly mined in Africa.b. Pencils were invented in 1603 by William Ledbelly.c. Even when sharpened, a pencil may not write as well as a pen.d. The substance used in pencils today is graphite.18. The Greek ideal of the hero most closely resembles today’s freeagentsuperstar.a. A superstar is an athlete who commands a great salary based onhis individual skills.b. The Greek warrior’s focus was on grasping at immortality, andhe did this by ensuring that his name would live on, long afterhe died.c. The Greek hero valued self-interest above loyalty to a cause, hisking, or to his army, just as the free-agent superstar values hiscontract salary above any special team, coach, or the game.d. The Greek hero was impressive in his performance on thebattlefield as well as in the sports arena.19. There is no instruction by the old bird in the movements of flight;no conscious imitation by the young.a. The most obvious way in which birds differ from humans inbehavior is that they can do all that they have to do, withoutever being taught.b. More extraordinary than the fact that a bird is able to flyuntaught, is that it is able to build a nest untaught.c. Young birds frequently make their first flights with their parentsout of sight.d. Young birds brought up in artificial environments will build theproper kind of nest for their species when the time comes.20. Parents play an important role in their children’s academic success.a. Video games have a negative impact on children’s academicsuccess.b. Studies show that children of parents who regularly assist withhomework and show an active interest in their child’s studiesbring home better grades.c. Studies show that watching less television and spending lesstime playing video games help children get better grades.d. Children who are avid readers get much better grades thantheir peers.21. In special cases, needy people who have nowhere else to go arepermitted to enter the United States as refugees.a. Other people, however, enter the United States illegally.b. The total number of newcomers was over one million.c. United States immigration laws put limits on the number ofpeople permitted to enter the United States.d. As many as 12 million people may be living in the United Statesillegally.22. Most common weed killers work by poisoning the root of the plant.a. Weed killer can be dangerous to pets.b. Some weeds can grow even during drought.c. When using weed killer, always wear gloves.d. The poison is absorbed by the leaves and carried down to theroots.