一个圆柱体的底面半径是2cm，它的侧面展开后是正方形，那么它的高是[ ]
A．4cm
B．8cm
C．12.56cm
D．无法确定
答案：C
Experts removed a layer of eighteenth-century red paint from a figure in a painting by a sixteenth-century Italian artist, revealing a layer of green paint underneath. Since the green paint dates from the sixteenth century, the figure must have been green, not red, when the painting was completed in 1563. Which of the following, if true, most seriously weakens the argument
A．The experts had been commissioned to restore the painting to the colors it had when it was completed.
B．X-rays reveal an additional layer of paint beneath the green paint on the figure.
C．Chemical analyses were used to determine the ages of the red paint and the green paint.
D．The red paint was added in the eighteenth century in an attempt to repair damage done in the late seventeenth century.
E．(E) Red paint on the robe of another figure in the painting dates from the sixteenth century.
以下不适用于空调新风系统设计的是( )。
A．进风管面积满足全新风要求 B．进风管装能严密关闭的阀门C．采用双层活动百叶进风 D．进风口设在排风口上风侧
