线路板设计中顶层丝印在哪一层（）。
A.25层
B.26层
C.27层
参考答案：B
用配方法解方程x2-4x-1=0配方后得到方程______．
All else being equal, a decrease in expected yield volatility would most likely cause the price of:（）
A. both a callable bond and a putable bond to decrease.
B. a callable bond to increase and the price of a putable bond to decrease.
C. a callable bond to decrease and the price of a putable bond to increase.
