Never stand up ________ you are asked to.
#58222
A
if
B
since
C
unless
D
when
推荐题目
It ______last week that the haze(雾霾) in Beijing caused many problems.
#56008
A
reports
B
reported
C
is reported
D
was reported
---How long have you known the doctor ? ---_________he helped me three years ago.
#56019
A
When
B
Before
C
Because
D
Since