—I called you at seven o’clock last evening, but nobody answered the phone.

—Oh, my husband and I __________ outside.

A. took a walk                 

B. have taken a walk          

C. were taking a walk

逻辑覆盖标准主要用于

A．黑箱测试方法

B．白箱测试方法

C．灰盒测试方法

D．软件验证方法