— When did the computer crash?    

— This morning, while I ______ the reading materials downloaded from some websites. [ ]

A. have sorted

B. was sorting

C. am sorting

D. had sorted

在热轧钢筋电弧焊接头拉伸试验中，（）个热轧钢筋接头试件的抗拉强度均不得小于该牌号钢筋规定的抗拉强度，并应至少有（）个试件是延性断裂。

A．3，2

B．2，1

C．3，3

D．2，2