我国的《环境空气质量标准(GB3095-1996)》对几种污染物制定了限值()
A.2种
B.4种
C.6种
D.9种
E.12种
参考答案:D
-May we leave the classroom now?
-No, you ______. You ______ to leave until the bell rings.
A.mustn’t, are allowed
B.don’t have to, are supposed
C.needn’t, aren’t allowed
D.can’t, aren’t supposed
()
A.A
B.B
C.C
D.D