问题
选择题
.________they were singing, the teacher came in.
A．Before
B．after
C．As
D．Until
答案
答案：C
表示正当什么时候，用as
搜题请搜索小程序“爱下问搜题”
.________they were singing, the teacher came in.
A．Before
B．after
C．As
D．Until
答案：C
表示正当什么时候，用as