根据GB18218-2000《重大危险源辨识》的规定，汽油属于（）。
A.爆炸性物质
B.易燃性物质
C.活性化学物质
D.有毒物质
参考答案：B
—Hey, boy! We should keep the park clean. You _________ throw litter about.
—Sorry, I won't do that again. [ ]
A. mustn't
B. needn't
C. couldn't
第三套人民币中1角面额的纸币有（）种版别。
A.2
B.3
C.4
D.5
