现在给出1、2、3、…、11、12这12个数，在其中某些数前面添加负号后，使这12个数的和为0，写出一个你认为正确的式子（ ）。
“略”（答案不唯一）
某导体两端电压为3伏时，通过该导体的电流为0.2安，则10秒内通过该导体横截面的电荷量为______库，电流做功为______焦．当通过该导体的电流为0.5安时，它的电阻为______欧．
Which of the following statements about the risks associated with investing in bonds is most accurate（）
A. Corporate debentures are not subject to prepayment risk.
B. Liquidity risk is not relevant if the portfolio manager intends to hold the bond to maturity.
C. All fixed income securities except short-term Treasury bills are subject to volatility risk to some degree.
