如图所示，用水平拉力F拉着物体A在水平方向上运动，当F=10N时，A恰好做匀速直线运动，当拉力F变为12N时，物体A受到的合力为________N。

--What did you say just now?

--I asked _______.

A．that I could open the door

B．could I open the door

C．how could I open the door

D．how I could open the door