一道关于情态动词的英语题
问题描述：
一道关于情态动词的英语题
He was a good swimmer so he _________ swim to the river bank when the boat sank.
A. couldB. mightC. shouldD. was able to
选D为什么不选A
强调能力不应该选择A吗？
答
be able to 强调结果,成功做成某事
could 强调能力,可能
The cildren were able to run out of the house before it was burnt down.