几个新概念英语书上的问题

题目

几个新概念英语书上的问题
第29课：
1.however,a new type of humour,which stems largely from u.s,has recently COME into fashion
Q：请问那里为什么用COME的原型呢?这是完成时态吗?
2.the following day,however,the doctor consoled him by telling him that his chances of BEING able to leave hospital in time for new year celebrations were good
Q:这里的BEING怎么理解?
第32课:
the sea bed was scoured WITH powerful nets .
Q：为什么用WITH呢,用BY可以吗?
能不能尽量通俗易懂的讲解一下动名词?

答案

是完成时
has come 没错
come的变化是 come-came- come
用的是过去分词 和原形形态一样
2.因为前面是介词of 所以后面要用动名词的形式
be 的动名词形式是being
3.with 强调用...
by 是被...
有时候可以互用的
动名词是动词后面加ing