has your grandpa lived here? --Since last year.A. How long B. How oftenC. How soonD. H

问题补充：

-- has your grandpa lived here? --Since last year.

A. How long

B. How often

C. How soon

D. How far

答案：

(答案→)A. How long

B. How often

C. How soon

D. How far

解析：根据答语可知询问的是时间段，故选A.