have trouble in doing have difficult in doing have problem in doing

问题描述:

have trouble in doing have difficult in doing have problem in doing
这三个固定搭配中trouble difficulty problem用加s 为什么
这三个固定搭配中trouble difficulty problem用加s吗 为什么

不用加,这是固定搭配,都表示困难做么事.再说困难没有什么可数的,而且这是习惯用语.