一般疑问句 Could you buy some while you 're out?
罗列事物 You can read books,listen to music,and surf the internet.
逗号前面最后一个词 Before airplanes,traveling took a long time.
引导词后面
如 however,in my opinion,on the other hand.
Actually,the job is really interesting.
选择疑问句“or”之前的部分 What water sports do you like,snorkeling or surfing?
