下列的物体受到不平衡力的是（　　）

A．停在地面上的汽车

B．在弯路上运动且快慢不变的汽车

C．匀速直线下降的直升飞机

D．匀速直线上升的电梯

The UN should _______the establishment of Iraqi government after the war, I think.

A．take part in

B．play a leading role in

C．play a role among

D．play a important part for