债券流动性越大，投资者要求的收益率越（）。
A．不变
B．高
C．低
D．不确定
参考答案：C
The meeting _____ for a week now.[ ]
A. has finished
B. has ended
C. has been over
D. has been in
分配阀上的安全阀有何作用？
