he start learning english since three years----.A.before B.a

B.ago,since后面加过去的时间.
不明白的再问哟,请及时采纳,多谢!
再问： 还是不懂 before不是暗示这完成时么
再答： He has learned English for three years before. 但在since后面加的就是具体的过去时间。