I spent half an hour( )this difficult math problem.

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问题 I spent half an hour( )this difficult math problem.

选项 A、having worked on
B、to work on
C、on work
D、working on

答案D

解析 习惯用法。spend some time(some money)in doing sth.(on sth.),如:She spent the whole afternoon shopping.她一下午都在购物。
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