He accidentally _____ he had quarreled with his wife and that he hadn’t been home for a couple of weeks.

A．let out

B．tried out

C．ran out

D．made out

面向对象系统的单元测试包括方法层次的测试、类层次的测试和类树层次的测试。在常见的测试技术中，______属于方法层次的测试，______属于类层次的测试。

A．等价类划分测试和多态消息测试
B．不变式边界测试和递归函数测试
C．组合功能测试和非模态类测试
D．不变式边界测试和模态类测试