问题补充：
When a pencil is partly in a glass of water, it looks as if ＿＿＿＿.
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：as if引导的从句，如果所说内容与事实不相符时，常用虚拟语气。此题是一种自然现象，故应用一般过去时。注意比较It seems/looks as if it is going to rain.(看起来天将要下雨。)
