SC 三个问题请教

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1. The Rorschzch test is gaining new respect as a diagnostic tool because it takes only one hour to expose behavior and thought processes (that may be unlikely to emerge in other procedures or weeks of ordinary interviewing.)
C. that might not emerge in other procedures or in weeks of ordinary interviews.
d. that may not emerge under other porcedures or weeks of ordinart interviews.

the answer is C. why not D?


2.During the Great Despression, industrial output fell by nearly fifty percent from its peak in 1929 down to its nadir in 1933.
B) During the Great Despression, industrial output fell by nearly fifty percent from its peak in 1929 to its nadir in 1933.
D: During the Great Despression, industrial output fell from its peak in 1929 to its nadir in 1933 by nearly fifty percent.

Answer is B, why not D?

The debate over billingual education centers on the issue of whether the US should foster the idea of a single common language, an idea, some believe, that has in the past (been crucial in binding diverse constituencies togther).
A.
D. become crucial in binding togther diverse constituencies

Answer is A. 可我觉得完成时中 BECOME 不是比BEEN要好吗？

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THANKS！