[单项选择]Three-fourths of the surface of the earth _______sea.
A. are
B. were
C. is
D. has been

[单项选择]If the temperature at the earth's surface is twenty degrees Fahrenheit, the temperature in a coal mine 500 feet below the surface would, in degrees, be _____________.
A. 50
B. 40
C. 30
D. 120

[单项选择]It has been estimated that the earth's surface temperature has increased ______ one quarter to three fourths of a degree since 1850.
A. by
B. at
C. to
D. with

[单项选择]In Earth's infancy, its surface was warm enough for life ____ the young Sun was fainter than it is today.
A. ( in spite of
B. ( whether
C. ( neither of which
D. ( even though

[单项选择]Without sun's light ______ the earth's surface, no life could exist on the earth.
A. warms
B. warmed
C. to warm
D. warming

[单项选择]Without the sun's light______the earth's surface, it would be so cold that life could not exist on the earth.
A. warms
B. warmed
C. warming
D. to warm

[单项选择]In most parts of the world the earth's surface______.
A. is hot
B. is cold
C. is water
D. has cracks

[单项选择]

All over the earth’s surface is a layer of air which extends upwards for many miles. This air (1) the oxygen without which neither plants nor animals (2) live. Its movements, temperature and pressure (3) the weather, and it is a vehicle (4) the clouds of water vapour (5) condense and fall as rain. It forms a blanket which (6) us from the extreme heat of the sun during the day and (7) the extreme cold when the sun has (8)
It is chiefly (9) air that sound travels, so that if there were no air we should (10) practically nothing. The atmosphere is held (11) the earth’s surface by the gravitational pull of the earth -- that.is, it has weight. High up it is thin (12) near the surface it is compressed by the (13) of air above, and is more dense. The weight of air pressing (14) each square inch of surface at sea-level is nearly (15) pounds, which meansthat the
A. at
B. to
C. against
D. after