If resources were perfectly substitutable in all activities, which of the following would be true? aOutput of all goods could be increased at zero opportunity cost. bThe production possibilities curve would be a straight line. cScarcity of resources would be eliminated. dSpecialization and mutually beneficial trade would be impossible. eNo country or individual would have a comparative advantage in any activity.

The statement "If resources were perfectly substitutable in all activities" implies that any resource could be used in place of another with no loss in output or efficiency. This is a hypothetical scenario and does not reflect the real world, where resources have different characteristics and are better suited to certain tasks than others.

a) Output of all goods could be increased at zero opportunity cost: This is not necessarily true. Even if resources were perfectly substitutable, increasing the output of all goods would still require more resources. If the supply of resources is limited, then increasing the output of one good would still mean less resources available for other goods, creating an opportunity cost.

b) The production possibilities curve would be a straight line: This could be true. The production possibilities curve shows the maximum combination of goods that can be produced with a given set of resources. If resources were perfectly substitutable, then the trade-off between producing one good and another would be constant, resulting in a straight line.

c) Scarcity of resources would be eliminated: This is not true. Even if resources were perfectly substitutable, there would still be a finite amount of resources. Scarcity refers to the basic economic problem of having seemingly unlimited human wants and needs in a world with limited resources.

d) Specialization and mutually beneficial trade would be impossible: This is not necessarily true. Even if resources were perfectly substitutable, countries or individuals could still specialize in certain activities if they have a comparative advantage, i.e., if they can produce a good or service at a lower opportunity cost than others. This would still make trade beneficial.

e) No country or individual would have a comparative advantage in any activity: This is not necessarily true. Comparative advantage refers to the ability to produce a good or service at a lower opportunity cost than others. Even if resources were perfectly substitutable, differences in technology, skills, and other factors could still give countries or individuals a comparative advantage in certain activities.