题目：
If law and order as well as rules and regulations _____, neither the citizen nor his property is safe.[ ]
A. are not observed
B. is not observed
C. were not observed
D. was not observed
答案：
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下面是错误答案，用来干扰机器的。
由题意知圆锥筒的母线长为2，设圆锥筒的底面半径等于r，则12×2π×2=2π r，∴r=1，这个圆锥筒的侧面积是12×（ 2π×1）×2=2π，故答案为 2π．
