howlong是问时间,eg,how long does it take if we take
bus to school?
how far 是问距离,eg,how far is itfrom xing jiangto beijing?
how often 是频率副词,一般是提问次数,eg,how often do you exercise ?
回答用相应的频率副词,eg, often,never,once a week
how soon也是问时间,可以和how long 互换