对失去氧化层的镁铝合金件必须在（）h内进行氧化处理。
A.10
B.12
C.24
D.48
参考答案：D
一个正三角形和一个正六边形周长相等，则正六边形面积为正三角形的（）
A．倍
B．1.5倍
C．倍
D．2倍
The less the surface of the ground yields to the weight of the body of a runner, () to the body.
A. the stress it is greater
B. greater is the stress
C. greater stress is
D. the greater the stress
倍
倍