Since 1970,millions of enthusiasts____Vitamin C,which they believe can remedy the common cold.

问题描述:

Since 1970,millions of enthusiasts____Vitamin C,which they believe can remedy the common cold.
A.have been taken B.have been taking

答案应为B
此句子主语是millions of enthusiasts(数以百万记的热心的人们),宾语是Vitamin C(维生素C),谓语动词应选择主动,该动作延续到现在,而且未必停止,所以应选择现在完成进行时态.
如果改成have taken 表明该动作到现在已经完成了,现在大家不服用维生素C了.根据实际情况来看,不太符合.如果改成have taken意思变成什么了?是不是也可以?我把答案改了,您看懂了吗?