地面效应可以（）.
A.增大桨叶角
B.增大旋翼转速
C.增大旋翼需用功率
D.增大旋翼拉力
参考答案：D
I don't know _______. [ ]
A. which one to choose
B. which one should I choose
C. how to do next
D. what to do it next
某企业年末应收账款余额为500000元，坏账准备账户贷方余额为2000元，按3‰提取坏账准备，则应计提的坏账准备为______
A．补提1500元 B．补提500元C．冲减500元 D．冲减3500元
