问题补充：
—May I open the window to let in some fresh air?
—
A. Come on.
B. Take care.
C. Go ahead!
D. Hold on!
答案：
A. Come on.
B. Take care.
(答案→)C. Go ahead!
D. Hold on!
解析：考查交际用语: A. Come on加油，B. Take care.保重，C. Go ahead!请便D. Hold on! 别挂断，句意是：--我可以打开窗户流通空气吗？选C合适，请便.
