问题
.It was _____ his mother came in _____ to prepare his lessons.
A:not until; did the boy begin
B:until; that the boy didn’t begin
C:until; did the boy not begin
D:not until; that the boy began
B:until; that the boy didn’t begin
C:until; did the boy not begin
D:not until; that the boy began
正确答案是：
