变压器能够改变（）。
Ａ.直流电压
Ｂ.交流电压
Ｃ.直流和交流电压
Ｄ.不能确定
参考答案：B
中厚皮片的厚度是（）。
A.0.1mm
B.0.2～0.25mm
C.0.8～1.0mm
D.0.35～0.8mm
E.1.2～1.5mm
A call market is least likely characterized as a market:（）
A. with bid-ask prices posted by dealers.
B. where buy-sell orders are cleared at a single equilibrium price.
C. with participation by a small number of active investors-traders.
