题干
School students _____ smoke because it is bad for their health and it is against the law.
A：needn't
B：couldn't
C：shouldn't
D：may not
答案(点此获取答案解析）
C
School students _____ smoke because it is bad for their health and it is against the law.
A：needn't
B：couldn't
C：shouldn't
D：may not
xC(g)+2D(g)，5min后反应达到平衡,容器内压强变小,已知D的平均反应速率为 0.1mol／(L·min),下列结论错误的是
铁溶液时，向试剂瓶中添加铁钉和少量稀硫酸；②用稀硝酸代替浓硝酸溶解、回收做银镜实验后试管内壁的银；③接触法制硫酸的设备中安装“热交换器”和锅炉，利用余热预热冷原料气和蒸气发电；④工业合成氨中分
离产物得到氢气和氮气再循环使用。上述主要不是从“绿色化学”角度考虑的是（ ）