Question

Mr. Green has made another wonderful discovery,  ______ great importance to science.

1. A.
   which I think is of
2. B.
   which I think it is of
3. C.
   that I think is of
4. D.
   I think which is of

Answer 1

A
考查非限制性定语从句。句意“格林先生又有精彩的发现了，我认为这个发现对科学有重要意义。”I think是插入语，可去掉；be of+抽象名词=抽象名词对应的形容词。B项的it多余；非限制性定语从句不能用that，排除C；引导词作主语不能省略，排除D；故选A。