问题
选择题
I worked on the problem ____ a long time and I worked it out ____ myself ____ last.[ ]
A. for; by; at
B. in; with; on
C. on; by; in
D. for; for; at the
答案
答案：A
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I worked on the problem ____ a long time and I worked it out ____ myself ____ last.[ ]
A. for; by; at
B. in; with; on
C. on; by; in
D. for; for; at the
答案：A