A; ——— will it take you to get to the post office? B; about half an hour 答案是how long

问题描述:

A; ——— will it take you to get to the post office? B; about half an hour 答案是how long
为什么不用how soon, 将来时态不是用how soon 吗

看答语about half an hour ,表示时间段的要用how long 提问.
如果把答语改为 In about half an hour ,就只能用How soon 了“还要多久”