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
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
答
3个词都是名词啊，动词+名词+介词。。。用a的话不符合美国人习惯 所以加s表复数
答
+s
答
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.