When a pencil is partly in a glass of water it looks as if it .A. breaks B. has brokenC.

问题补充：

When a pencil is partly in a glass of water, it looks as if it .

A. breaks

B. has broken

C. were broken

D. had been broken

答案：

A. breaks

B. has broken

(答案→)C. were broken

D. had been broken

解析：考察虚拟语气。 as if引导的从句如果表示的是虚假的事情，则常用虚拟语气.表示现在用一般过去时,如果是动词be,无论主语是单数还是复数一律用were.表示过去用过去完成时;表示将来用过去将来时.句意：当一支铅笔的一部分放在水杯里，看起来好像铅笔是断的。根据句意可知实际上铅笔并没有断。这是一个虚假的事情，且这是一个与现在事实相反的虚拟语气，故使用were。故C正确。