but it rains sometimes 为什么没有系动词

but it rains sometimes 为什么没有系动词 but it rains sometimes.句中rains为何是复数? sometimes it rains 为什么填rains而不填rain? but it rains sometimes中it表示的意思 it rains sometimes sometimes it rains和it rains sometimes 是不是一样的? It is always warm in April and May,but it rains sometimes 英语：it rains sometimes这句子中sometimes为什么放在句末?不是有动前系后吗? the it often rains,sometimes it rains quiet______ It never rains but it It rains sometimes可以说It is sometimes rain 这几个词为什么要加s1,It rains sometimes .2,It snows sometimes.3,The s