補充題第十題

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
答案是B。

我想請問一下 D的答案  有哪裡錯

還有怎麼知道  B中要用完成式  謝謝

there be结果不优选

这里完成时表示一种状态吧，应该没有错，比较所有选项还是b好