1.how soon 指再过多久,多久以后,主要用来对表示将来的一段时间常用于将来时 .(常用in短语回答如in an hour,in two weeks 等)提问,
2.how long指多长时间,主要用来对一段时间(如three days,four weeks 等)提问
1.—___（How soon）__will you be away?—In a couple of weeks.A.What time B.How soon C.How often D.How long
2.—Xiao Wang,__（how long）__will it take to fly to Guangzhou?—Sorry,I don’t know A.how far B.how soonC.how many