问题
选择题
For a long time, he hesitated whether he should tell us ____ what had happened.
A．at dusk
B．at length
C．at present
D．at stake
答案
答案：B
考查短语辨析。at dusk在黄昏，at length最后，详尽地，at present现在，at stake生死攸关，句意：很长一段时间，他犹豫是否他应该详尽地告诉我们所发生的事。故选B。