what do you usually do on rainy days为什么要用on而不用in?

what do you usually do on rainy days?答什么 I usually watch Tv on rainy days.为什么要用on,不用in? 下雨天你通常干什么?What do you usually do _on_ rainy day?为什么用on what do you usually do ____ school days?A.on B.in C.on D./ What does he he usually do on sundays?为什么这里用does/而不用do? 英语翻译（ ）1.What do you do _______ rainy days?A.in B.at C.on D. what do you usually do on the evening of Halloween?为什么是on 而不 on rainy days 为什么介词要用on而不是in? what do you usually do on weekends 为什么加s what do you do on these days What do you usually do on weekends? What do you usually do on vacation?用英文回答