求助NN大全748

elainesme

748. The fear of rabies is well founded; few people are known to recover from the disease after the appearance of the clinical symptoms.

(A) few people are known to recover from the disease after the appearance of the clinical symptoms

(B) few people are known to have recovered from the disease once the clinical symptoms have appeared

(C) there are few known people who have recovered from the disease once the clinical symptoms have appeared

(D) after the clinical symptoms appear, there are few known people who have recovered from the disease

(E) recovery from the disease is known for only a few people after the clinical symptoms appear

这个题我选的是A

不明白B里面once后为什么要用完成时态；known to recover和known have to recover 的区别是什么？？

joe11

现在完成时表示动作从过去开始，持续过一段时间。

90.   Since 1986, when the Department of Labor began to allow investment officers’ fees to be based on how the funds they manage perform, several corporations began paying their investment advisers a small basic fee, with a contract promising higher fees if the managers perform well.

(A) investment officers’ fees to be based on how the funds they manage perform, several corporations began

(B) investment officers’ fees to be based on the performance of the funds they manage, several corporations began

(C) that fees of investment officers be based on how the funds they manage perform, several corporations have begun

(D) fees of investment officers to be based on the performance of the funds they manage, several corporations have begun（D）

(E) that investment officers’ fees be based on the performance of the funds they manage, several corporations began

The clause beginning Since 1986... indicates that the practice described in the second clause continued for some period of time after it began. Choice D, the best answer, supplies the present perfect have begun, which conveys this continuity;

Ａ中没有　has, 就没有持续的概念。

sensornet

感觉once后面的不用过去完成时也行。关键是are known to have recovered，我觉得这个have一定要加。多读几遍，感觉句子的意思。有时不需要执著的去考虑在语法上是否可行。