题目内容
This doubt had been in my mind for some time, but the research still went on _________ some reasons．
[ ]
A．
to
B．
about
C．
for
D．
in
答案：C
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题目内容
This doubt had been in my mind for some time, but the research still went on _________ some reasons．
to
about
for
in
A．to B．about C．for D．in