there firemen are very helpful 变单数句
问题描述：
there firemen are very helpful 变单数句
答
Fireman is very helpful.
本句子为主系表结构，主要的就是men改为man（复数变为单数）《主语》，are改为is（复数变为单数）《系动词》
答
this fireman is very helpful
答
This fireman is very helpful
或者The fireman is very helpful~
答
The fireman is very helpful.