Question

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

Answer 1

B

考查介詞。work on從事，忙于；work out解決。句意：他已經做那條數學問題接近1個小時了，但他還沒有做出來。