一、单选题（本大题共15小题，共15.0分）
1. When _______ the two countries, we’ve found they have much in common.
A. compared B. compare C. being compared D. comparing
【答案】D
【解析】
【详解】考查省略句。句意：比较这两个国家时，我们发现它们有许多共同之处。在when, while, if, as if, though(或although), as, until, once, whether, unless, where等连词连接的状语从句中，常省略跟主句相同的主语和be动词。从句完整为When we are comparing the two countries。省略主语与be动词，故选D。
【点睛】状语从句中的省略
(1)在when, while, if, as if, though(或although), as, until, once, whether, unless, where等连词连接的状语从句中，常省略跟主句相同的主语和be动词。如：
When (water is) pure, water is a colorless liquid. 水纯净时，是无色的液体。
When (I am) in trouble I always turn to her for help. 我困难时总是找她帮助。
Errors, if (there are) any, should be corrected. 如果有什么错误，就应当改正。
Wood gives much smoke while (wood is) burning. 木头燃烧时放出大量烟雾。
The letter is to be left here until (it is) called for. 这封信留在这里待领。
Henry looked about as if (he were) in search of something. 亨利向四周环视，似乎在寻找什么。
She studies very hard though (she is) still rather weak. 她尽管体弱，但学习仍十分努力。
(2)“when(或if, where, wherever, whenever, as soon as, as fast as, than等)+possible/necessary等”，中间省略了it is(或was)。如：
Answer these questions, if (it is) possible without referring to the book. 如果有可能，请不看书回答这些问题。
When (it is) necessary you can help us to do something. 必要时你可以帮助我们做些事。
