It rains off and on.
断断续续地下着雨.
They waited for something to turn up.
他们等待着发生什么情况.
The average PE during the period was 30.
而在这期间的平均本益比是30
Bad habits are developed over time.
坏的习惯随着时间慢慢滋生.thank不客气，要采纳哦