货叉是叉车的重要构件，（）要求截面小，重量轻。
A.经常调整
B.经常更换
C.载货体积大
D.受力大
参考答案：D
夹层动脉瘤最有特征的声像图是：()
A．双腔征
B．血栓
C．狭窄的腔
D．内膜瓣
E．动脉壁溃疡形成
(2012·福建，30)It is hard for the Greek government to get over the present difficulties ________ it gets more financial support from the European Union.
A．if
B．unless
C．because
D．since
