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.
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.加热小麦仁毁坏了的发酵生面团所必须的谷胶
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
The stimulus says that the discovery of yeast to leaven bread dough happens at the same time that a new variety of wheat was found. The new wheat is edible without toasting.
The question stem ask you to find an answer choice which support a causation between the two events.
C says that a protein required for yeast to leaven bread dough is destroyed during toasting. That ensures that before the introduction of the new wheat, yeast could not leaven bread dough made from toasted wheat. Once the new wheat was found, its edible part could be separated without heating so that the protein required for yeast to work would be present in the bread dough. This supports the hypothesis that yeast was discovered because a new wheat was introduced.作者: jessicasonia 时间: 2012-4-8 19:57
多谢LZ 如此清晰的解释~！
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