— How long _____ Mr Li _____ you English, Daming?

— For three years. [ ]

A. does; teach

B. did; teach

C. has; taught

D. are; teaching

有梅毒感染史，无任何梅毒性的临床症状和体征，多见于（）

A.一期梅毒

B.二期梅毒

C.三期梅毒

D.潜伏梅毒

E.先天梅毒