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Q20:

Which of the following most logically completes the reasoning?

Either food scarcity or excessive hunting can threaten a population of animals. If the group faces food scarcity, individuals in the group will reach reproductive maturity later than otherwise. If the group faces excessive hunting, individuals that reach reproductive maturity earlier will come to predominate. Therefore, it should be possible to determine whether prehistoric mastodons became extinct because of food scarcity or human hunting, since there are fossilized mastodon remains from both before and after mastodon populations declined, and ______.

there are more fossilized mastodon remains from the period before mastodon populations began to decline than from after that period
the average age at which mastodons from a given period reached reproductive maturity can be established from their fossilized remains
it can be accurately estimated from fossilized remains when mastodons became extinct
it is not known when humans first began hunting mastodons
climate changes may have gradually reduced the food available to mastodons

Answer: B

Q40:

Agricultural societies cannot exist without staple crops. Several food plants, such as kola and okra, are known to have been domesticated in western LACE>AfricaLACE>, but they are all supplemental, not staple, foods. All the recorded staple crops grown in western LACE>AfricaLACE> were introduced from elsewhere, beginning, at some unknown date, with rice and yams. Therefore, discovering when rice and yams were introduced into western LACE>AfricaLACE> would establish the earliest date at which agricultural societies could have arisen there.

Which of the following is an assumption on which the argument depends?

People in western LACE>AfricaLACE> did not develop staple crops that they stopped cultivating once rice and yams were introduced.
There are no plants native to western LACE>AfricaLACE> that, if domesticated, could serve as staple food crops.
Rice and yams were grown as staple crops by the earliest agricultural societies outside of western Africa.
Kola and okra are better suited to growing conditions in western Africa than domesticated rice and yams are.
Kola and okra were domesticated in western Africa before rice and yams were introduced there.