IT WAS NOT _______ HIS FATHER CAME HOME THAT THE BOY DID HIS HOMEW...

13. - DE KIEM TRA SO 410 DUC CANHQUANGLA
DE KIEM TRA SO 410 DUC CANHQUANGLA

13. It was not _______ his father came home that the boy did his homework.

A. as

B. when

C. until

D. till