比例式减压阀的减压比不宜大于______。
A．3:1 B．1:3 C．1:5 D．5:1
参考答案：A
In England it is polite to _____. [ ]
A. point at somebody
B. eat half of the food
C. leave something in the bottle
D. finish eating something
急性硬脑膜下血肿的CT表现特征是（）
A.新月形高密度灶
B.梭形高密度灶
C.新月形稍低密度灶
D.脑内高密度灶
E.骨板下圆形高密度灶
