Question

He is rather difficult to make friends with，but the friendship of his，once ________, is more true than any other．

1. A.
   gained
2. B.
   to gain
3. C.
   having gained
4. D.
   gain

Answer 1

A
解析：
once可引導(dǎo)時(shí)間狀語從句表?xiàng)l件，意思是“一旦……”.此空填gained，其前省略了it is.在時(shí)間、條件、讓步狀語從句中，如果從句的主語和主句的主語相同，從句中謂語動(dòng)詞義含有be的某一種形式，可以省略從句中的主語或be動(dòng)詞.答案為A．例如：Once seen，it will never be forgotten．一旦見到，就永遠(yuǎn)不會忘掉.The research is so designed that once begun nothing can be done to change it．調(diào)查是預(yù)先計(jì)劃的，一旦開始就無法改變.