Question

---How long have you been learning Japanese?
---I’ve been learning it ____________.

A．when I was 10 years old	B．since 10 years ago
C．for 10 years old	D．in 10 years

Answer 1

B

考察时态，根据前文我已经学了……现在完成时，能够和since +一段时间 ago或for+一段时间连用，故选B。