In 2000, a mere two dozen products accounted for
half the increase in spending on prescription drugs, a phenomenon that is explained not just because of
more expensive drugs but by the fact that doctors are
writing many more prescriptions for higher-cost drugs.
(E) in attributing a food allergy as the cause of
criminal or delinquent behavior,
(A) a phenomenon that is explained not just because of more expensive drugs but by the fact that doctors are writing
(B) a phenomenon that is explained not just by the fact that drugs are becoming more expensive but also by the fact that doctors are writing
(C) a phenomenon occurring not just because of drugs that are becoming more expensive but because of doctors having also written
(D) which occurred not just because drugs are becoming more expensive but doctors are also writing
(E) which occurred not just because of more expensive drugs but because doctors have also written
这题选择A, 我对选择答案没有疑问。但是有一个点是 doctors are writing 这个问题
present progressive is the action on goin gin the present time frame
这题通过逻辑意思，我该怎么判断doctors 是用are writing 而不是用present perfect：have written?
这个事件是发生在 2002， a phenomenon is explained用的是present tense， 在这里，是不是phenomenon，theory, secintific rearch都用present tense? 是否代表后边得都要用present tense?
OG上类似的例子：
Last week local shrimpers held a news conference to take some creditfor the resurgence of the rate Kemp's ridley turtle, saying that theircompliance with laws requiring turtle-excluder devices on shrimp nets isprotecting adult sea turtles.
关于这题的时态ron的回答：
first, note that this is a non-issue in this problem, as you are not required to make a decision about tenses. (there are only two choices that are not in the present progressive -- (a) and (c) -- and both of those have subject-verb disagreement.)
second, no, this construction doesn't require the present perfect (...and you know it doesn't, because the official answer doesn't have it).
the present perfect gives the impression that something has happened in the past, in a way that
* has persisted up to the present,
* still affects the present even though it's over, OR
* is over, but could happen again.
if the sentence is meant to emphasize that the action is actually ongoing IN the present timeframe, then the present perfect is not the correct tense to use -- the present perfect (despite its name) does not necessarily indicate that the action continues through the present timeframe.
this is, in fact, the only main function of the present progressive (is/are -ING) tense, which is therefore an excellent choice for this sentence.作者: imddung 时间: 2013-5-17 20:51
