成熟卵泡破裂，释放出其中的卵细胞、卵泡液和一部分卵泡细胞的过程称为（）
A.受精
B.卵裂
C.囊胚形成
D.排卵
E.桑椹胚形成
参考答案：D
The film _____ for ten minutes when I got to the cinema. [ ]
A. has been on
B. had started
C. had been on
D. had begun
按照净现值的计算公式，当各年现金流量不变，而折现率提高时，净现值应该( )。
A．不变
B．提高
C．提高或降低
D．降低
