老版本og（第十版）80的题目，请问E选项如何取非

inferno19

80.Theprogram to control the entry of illegal drugs into the country was a failure in1987. If the program had been successful, the wholesale price of most illegaldrugs would not have dropped substantially in 1987.

Theargument in the passage depends on which of the following assumptions?

(A)The supply of illegal drugs dropped substantially in 1987.

(B)The price paid for most illegal drugs by the average consumer did not dropsubstantially in 1987.

(C)Domestic production of illegal drugs increased at a higher rate than did theentry of such drugs into the country.

(D)The wholesale price of a few illegal drugs increased substantially in 1987. E

(E) Adrop in demand for most illegal drugs in 1987 was not the sole cause of thedrop in their wholesale price.

og说：If the drop in price was caused by a drop in demand, there is no reason to suspect that there has been any increase in supply caused by drugs entering the country

请问这个怎么理解？

如果E选项是There was a substantial drop in the demand of illegal drugs in 1987.是不是也是正确的？因为我觉得如果对E选项取非，应该是这样？！：
A drop in demand for most illegal drugs in 1987 was the sole cause of the drop in their wholesale price.

cdwayne

A drop in demand for most illegal drugs in 1987 was not the sole cause of thedrop in their wholesale price.
取非把not去掉即可。

價錢下跌有兩種，供大於求，題目假設政府失敗，即供應量大，(E) 假設需求量小非唯一原因，否則的話，政府有可能控管成功，而跌價原因純粹是因為需求變小。不知道這樣說明清不清楚。

inferno19

多谢！我误以为题干中第一句是个背景信息...

skyemotion

假设条件排除了其他可能性啊。