they have been trapped for seventeen hours. they tried to come up seventeen hours___
问题描述：
they have been trapped for seventeen hours. they tried to come up seventeen hours___
Asince B ago C for D since then
选择哪一个,及分别说出每个为什么对与错,
答
句子的意思是：他们被困了17个小时,他们17个小时前就开始尝试如何逃离困境.
选B