How often意思是:多久（一次）：用来询问谓语动词所表示的动作发生的频率,即单位时间内发生的次数。例如，
How often do you go swimming?你多久去游泳一次？
How often do you go riding?你多长时间骑一次马？
How often do you brush your teeth?你多久刷一次牙？
How often do you go to the theatre ?你多久看一次戏？
How often do you do housework?你多长时间做一次家务？
How often do you have a bath?你多久洗一次澡？
