题干
Advertising is different from other forms of communication in that the advertiser pays for the message .
A：to deliver
B：delivered
C：to be delivered
D：delivering
答案(点此获取答案解析）
C
；② 
；③ 
；④ 
，观察你计算的结果，用你发现的规律直接写出下面式子的值： 
=