737－300型飞机的减震支柱里充的气体是：（）.
A.压缩空气
B.干燥的空气
C.氮气
D.干燥的空气或氮气
参考答案：D
细胞向外界吸收水分，在液泡形成前主要是吸胀作用。( )
The cargo must be shipped directly to China, that is ( ) is not allowed.
A．partial shipment
B．transshipment
C．through shipment
D．total shipment
