twotimes前面用什么介词

two times前面用介词for，例如：

1、I have been to China for two times.我来中国两次了。

2、Listen to the dialogue and read it for two times.听和读是提高学生英语能力所必须的。

3、The Yong Pioneers the rooms for two times a week.少先队员们为老人门一周两次打扫房间。