问题补充：
The windows after school is over.
A. usually close
B. usually closed
C. are usually closed
D. are usually closing
答案：
A. usually close
B. usually closed
(答案→)C. are usually closed
D. are usually closing
解析：句意：在放学后，窗户通常是关着的。结合语境可知本句主语是动作对象，故用被动语态。选C。
