过敏毒素作用是
A.C1-C3B.C1-C4C.C3bD.C5b6E.C3a `
参考答案:E
Why didn't you tell me there was no meeting today? I______ all the way here through the heavy snow.
A.needn't have driven
B.can't have driven
C.mustn't have driven
D.shouldn't have driven
Try _____ she might, Sue couldn’t get the door open.
A.if
B.when
C.since
D.as