【单选题】关于肺表面活性物质,下列哪项是正确的( )。
A.
肺表面活性物质缺乏不是引起新生儿肺透明膜病的主要原因
D.
肺表面活性物质在胎龄24周时出现,35周迅速增加
【单选题】An axial piston pump differs from a radial piston pump as the pistons of an axial piston pump are positioned _____.
A.
radially from the shaft
B.
parallel to each other and to the shaft
C.
parallel to each other but at a right angle to the shaft
D.
at an angle to each other and to the shaft
【单选题】The function of the piston rings is to ________.
A.
help cool the piston by transferring heat from the piston to the cylinder wall
B.
provide a sliding seal between the piston and cylinder wall
C.
scrape oil off the cylinder wall as the piston moves down on the power and intake strokes.
【单选题】关于肺表面活性物质,下列哪项是正确的( )
A.
肺表面活性物质缺乏不是引起新生儿肺透明膜病的主要原因
D.
肺表面活性物质在胎龄18-20周时开始产生,35~36周达肺成熟水平
【单选题】Piston cooling fins are located
B.
beneath the piston crown
C.
at the base of the piston skirt
D.
inside the cylinder liner cooling water jacket
【简答题】Engine is the power source of the automobile. Power is produced by the linear motion of a piston in a cylinder. 英译汉: