几道逻辑题，求指教~~~

梓子

Agricultural societies cannot exist without staple crops. Several food plants, such as kola and okra, are known to have been domesticated in western Africa, but they are all supplemental, not staple, foods. All the recorded staple crops grown in western Africa

were introduced from elsewhere, beginning, at some unknown date, with rice and yams. Therefore, discovering when rice and yams were introduced into western Africa 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?

A.People in western Africa did not develop staple crops that they stopped cultivating once rice and yams were introduced.

B.There are no plants native to western Africa that, if domesticated, could serve as staple food crops.

C.Rice and yams were grown as staple crops by the earliest agricultural societies outside of western Africa.

D.Kola and okra are better suited to growing conditions in western Africa than domesticated rice and yams are.

E.Kola and okra were domesticated in western Africa before rice and yams were introduced there.
答案是A
Yeasts capable of leavening bread are widespread, and in the many centuries during which the ancient Egyptians made only unleavened bread, such yeasts must frequently have been mixed into bread doughs accidentally. The Egyptians, however, did not discover leavened bread until about 3000 B.C. That discovery roughly coincided with the introduction of a wheat variety that was preferable to previous varieties because its edible kernel could be removed from the husk without first toasting the grain.（求解释）



Which of the following, if true, provide the strongest evidence that the two developments were causally related?



A.Even after the ancient Egyptians discovered leavened bread and the techniques for reliably producing it were well known, unleavened bread continued to be widely consumed.

B.Only when the Egyptians stopped the practice of toasting grain were their stone-lined grain-toasting pits available for baking bread.

C.Heating a wheat kernel destroys its gluten, a protein that must be present in order for yeast to leaven bread dough.

D.The new variety of wheat, which had a more delicate flavor because it was not toasted, was reserved for the consumption of high officials when it first began to be grown.

E.Because the husk of the new variety of wheat was more easily removed, flour made from it required less effort to produce

Yeasts capable of leavening bread are widespread, and in the many centuries during which the ancient Egyptians made only unleavened bread, such yeasts must frequently have been mixed into bread doughs accidentally. The Egyptians, however, did not discover leavened bread until about 3000 B.C. That discovery roughly coincided with the introduction of a wheat variety that was preferable to previous varieties because its edible kernel could be removed from the husk without first toasting the grain.（求解释）



Which of the following, if true, provide the strongest evidence that the two developments were causally related?



A.Even after the ancient Egyptians discovered leavened bread and the techniques for reliably producing it were well known, unleavened bread continued to be widely consumed.

B.Only when the Egyptians stopped the practice of toasting grain were their stone-lined grain-toasting pits available for baking bread.

C.Heating a wheat kernel destroys its gluten, a protein that must be present in order for yeast to leaven bread dough.

D.The new variety of wheat, which had a more delicate flavor because it was not toasted, was reserved for the consumption of high officials when it first began to be grown.

E.Because the husk of the new variety of wheat was more easily removed, flour made from it required less effort to produce