long一般是说某种物质的长度,而 far是说距离的长度.
A:How long have you had it?你拥有它多长时间了?
此句中的had不可换成bought.与How long连用的动词必须是“延续性动词.”
eg.How long have you been here?你在这儿多久了?
How long have you been in the army?你在部队服役多久了?
注意和how soon,how far,how often比较：
how soon 意为（从现在起）再过多久,句子一般用将来时； how far 问路程“多
远”； how often 是问频率“间隔多久（一次）”； how long 是问（时间）“持续多久”,常与现在完成时或一般将来时连用.
eg.How soon can you finish the work?再过多久你能完成这项工作?
How far is it from Beijing to Guangzhou?从北京到广州有多远?
;How often do you go to see your grandparents?
;I go to see them every three weeks.
;你多长时间去看一次你的祖父母?
;每隔三周去一次.
How long are you going to stay in Shanghai?你将在上海呆多久?
