英语：主语是动名词
课本上的例句：
1.Designing clothes is not a man's job.
2.Being a flight attendant sounds exciting.
3.Writing a gossip column could be fun.
4.Directing a TV show would be interesting.
为什么前面的第一个动词都加ing?直接用原型不行吗?
麻烦英语好的朋友帮忙解释下,我初学英语,