问题
选择题
27. The boy was busy doing his homework, only_____once in a while to look out of the window.
A．stopping
B．to stop
C．stopped
D．having stopped
答案
答案：A
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27. The boy was busy doing his homework, only_____once in a while to look out of the window.
A．stopping
B．to stop
C．stopped
D．having stopped
答案：A