《中学生守则》规定中学生不准吸烟，这是因为吸烟有害身体健康。吸烟吸入有毒害的物质是[ ]

A.一氧化碳

B.甲醛

C.黄曲霉素

D.二氧化碳

The traffic is not busy now. We _____ arrive before dark. [ ]

A. should

B. mustn't

C. need

D. can't