求解一道题啊啊啊啊啊！

alex219

今天让一同学给问蒙了，请问大家这题怎么做！！！


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

cocoloop

选E~经典的题~
one 作explosion的同位语，是对explosion的补充说明。one that they believe to be of a type...  that之后是定语从句修饰one.还原后的句子是they believe one to be of a type...其中one在定语从句中作宾语，所以that可以省略。至于为什么用to be of a type...因为要注意概念对等性，explosion和a type在概念上不对等，可以理解为explosion包含于type中。例子：The agricultural films were of special interest to us.