到底是on their vacation 还是 for their vacation啊?求解!

到底是on their vacation 还是 for their vacation啊?求解! 到底是on holiday还是in holiday那是（ ）vacation，括号中填介词 go to vacation 和go on vacation 那个是度假 请问是in summer vacation还是on summer vacation? 是travel to vacation,还是travel on vacation 是in vacation,还是on vacation,还是atvacation? 是go on vacation 还是go on a vacation?是go for vacation还是go for a vacation? there are many people on vacation对吗有什么例句是be on vacation 是on vacation还是on a vacation 它们有什么区别? when is he going on vacation为什么用on vacation,难道是正在度假中吗? They are going to Hainan( )their vacation.A.on B.in C.for D.to Since our parents are on their vacation,we have to look after ourselves in the vacation ；go on vacation ；on vacation 区别? go on vacation , on a vacation是什么意思 on vacation(翻译） on vacation 造句 on a vacation造句