单项选择题

How is crude oil brought to the surface

A．By expansion of the hydrocarbons.
B．By pressure and pumping.
C．By vacuum created in the drilling pipe.
D．By expansion and contraction of the earth's surface.

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单项选择题

Which of the following is TRUE

A．The various petroleum products are produced by filtration.
B．Heating and condensation produce the various products.
C．Chemical separation is used to produce the various products.
D．Mechanical means such as the centrifuge are used to produce the various products.

单项选择题

In order to continue the marriages of the shiftworkers,______.

A．wives must learn to care for the children when their husbands are absent
B．shiftwork couples must administer their time and activities
C．wives mustn't adapt their own feelings of boredom to their husbands' work
D．all of these