通过在冷冻水泵和冷却水水泵加装变频器，节能效果在（）以上。
A.20%
B.40%
C.60%
参考答案：B
According to the Standards of Professional Conduct relating to record retention, if local regulatory guidance is in place and requires at least 5 years of maintenances, CFA members should keep records for at least:（）
A. 5 years.
B. 7 years.
C. 10 years.
如果外汇银行卖出某种外汇的数额超过买入的数额，则称该银行对该种货币( )。
A．空头
B．超买
C．多头
D．平仓
