sometimes it rains 为什么填rains而不填rain?

sometimes it rains和it rains sometimes 是不是一样的? Sometimes it rains q____ heavily. sometimes it rains 为什么填rains而不填rain? but it rains sometimes.句中rains为何是复数? sometimes when it rains谁唱的 Sometimes it rains heavily.可以改写成Sometimes there is___rain sometimes when it rains小提琴谱神秘园《sometimes when it rains》的小提琴谱 but it rains sometimes 为什么没有系动词but it's rains sometimes 可以么 the it often rains,sometimes it rains quiet______A.big B.small C.heavy D.heavily It rains sometimes and trees and grass turn green in it,always,hot,is,summer,and,in,sometimes,rains, Sometimes it rains quite -----.填什么,h 开头的... 填空：sometimes it rains ___in Xi'an in summer It sometimes rains in my hometown的同义句___ ___it rains in my hometown. 神秘园 sometimes when it rains谁有sometimes when it rains这首音乐的英文演唱版有的话发邮箱893960286 it sometimes rains in my hometown将其改为同义句：___ ___it rains in my hometown. it always hot is summer and in sometimes rains it用这些词造句 新概念英语1第51课的问题it rains sometimes可以把sometimes放到rains前面吗?为什么?为什么有的副词就能放到动词之前 谢谢!