— John failed his final exam.

— I'm not surprised at the news ______. ______, he is never seen busy with his lessons. [ ]

A. at all, After all

B. in all, After all

C. above all, In all

D. at all, In all

如图所示，质量分别为m₁、m₂的两个物体通过轻弹簧连接，在力F的作用下一起沿水平方向做匀加速直线运动（m₁在光滑地面上，m₂在空中），力F与水平方向的夹角为θ．则m₁的加速度大小为（　　）

A．

B．

C．

D．