It________we had stayed together for a  couple of    weeks_______I found we had a lot in common.   [ ]

A. was until; when    

B.was until; that    

C. wasn't until; when    

D.wasn't until; that

______降低了面向对象软件的数据被任意修改和读/写的可能性，减少了传统测试中对数据非法操作的测试。

A．封装性
B．继承性
C．多态性
D．重用性