_______ I walked into class, the teacher had started teaching already.
A:By the time
B:While
C:After
D:Because
ch____ck____n
用所给词的适当形式填空
给下列加下划线的字注音或根据拼音写汉字。
____
黝黑
黯然
禁锢
zhì
xī
zèng
____留
____利
____亮
1991年世界贸易组织成立,英文简称是WTO。( )