how often的用法例句：

　　He was shocked at how often she used the F-word.

　　她常常使用粗俗的罵人話，這使他感到震驚。

　　How often do you give your phone number out?

　　你經(jīng)常把自己的電話告訴別人嗎？

　　No matter how often they turn up, their welcome never wears out.

　　不管他們多久露面一次，都永遠那么受歡迎。

　　I don't know how often I heard the same awful jokes

　　這種千篇一律的爛笑話我不知道聽過多少回了。

　　How often does it need to be changed?

　　大概要多久換一次呢？