[求助] 请教 NN: og 9

priscelia

9. Astronomers at the Palomar Observatory have discovered a distant supernova explosion, one that they believe is a type previously unknown to science.
(A) that they believe is
(B) that they believe it to be
(C) they believe that it is of
(D) they believe that is
(E) they believe to be of

og 中对于  A,B 中 one  和 that 的解释,我不是太明白. one 作代词,它后面用定语从句来修饰, that 为何要省掉呢, 不是在og 和 LZM 语法上有很多例子, 定从that 省是错的吗? 什么时候要省,什么时候不能省呢? 谢谢了!

hougang

priscelia：

去下面的网页去找你的答案。

http://forum.chasedream.com/dispbbs.asp?boardID=23&ID=27472&page=1

priscelia

谢谢了!

但看了讨论, 众说纷云,也没有结果呀!