couldn't=wasn't able ;weren't able 都是表过去时吗?有什么区别的?

问题描述:

couldn't=wasn't able ;weren't able 都是表过去时吗?有什么区别的?

个人认为是这样的,都表示过去,couldn't表示你有能力去做,但是主观上你不去做.wasn't able ;weren't able to就是你想去做,可是你没有能力去做.