He has worked the maths problem for nearly an hour but he simply can’t work it.On ;atB. on

发布时间：2020-08-16 17:52:38

He has worked      the maths problem for nearly an hour but he simply can’t work it    .
On ;at           B. on ;out            C. at ;up              D. for ;out

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解析：考查介词。work on从事，忙于；work out解决。句意：他已经做那条数学问题接近1个小时了，但他还没有做出来。
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