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？