how often后加过去时和一般现在时态中，不用于将来时；
how often
多长时间一次；
often
时常;常常;往往;大多
How often do you use the bus?
你多长时间坐一次公共汽车？
How often do you go to the theatre?
你多长时间看一次戏？
How often do you go swimming?
你多久去游泳一次？
How often do you exercise?
你多长时间锻炼一次？
