【C8】A．Despite the factB．Whatever it isC．No matter howD．Whether or not

【C7】

A．time

B．desire

C．agency

D．means

【C6】

A．works out

B．leaves out

C．runs out

D．puts out

【C5】

A．in

B．of

C．at

D．for

【C4】

A．profit

B．cost

C．budget

D．facility

【C3】

A．inherent

B．evident

C．large-scale

D．hidden

【C2】

A．admire

B．assure

C．assert

D．anticipate

In the fourth sentence of Paragraph 1, the word "outdated" can be best replaced by

A．unacceptable

B．banned

C．old-fashioned

D．rejected

This passage intends to______.

A．tell us why the gravitational pull is important

B．research on the problem of rocket travel

C．tell us how to conquer more of outer-space

D．discuss something between the Earth and the Moon

The word "precise" in precise calculations means______.

A．good guesses

B．simple problems

C．big errors

D．exact

er more and more of outer-space.Heres why. As a rocket leaves the Earth, the pull of the Earth on it becomes less and less as the rocket roars out into space.If you imagine a line between the Earth and the Moon, there is a point somewhere along that line, nearer to the Moon than to the Earth, at which the gravitation pull of both the Earth and the Moon on an object is just about equal.An object placed on the Moon side of that point would be drawn to the Moon.An object placed on the .Earth side of that point would be drawn to the Earth.Therefore, a rocket need be sent only to this "point of no return" in order to get it to the Moon.The Moons gravity will pull it the rest of the way. The return trip of the rocket to the Earth is, in some ways, less of a problem.The Earths gravitational field reaches far closer to the Moon than does the Moons to the Earth.Thus it will be necessary to fire an Earthbound rocket only a few thousand miles away from the Moon to reach a point where the rocket will drift to the Earth under the Earths gravitational pull. The problem of rocket travel is not so much concerned with getting the rocket into space as it is with guiding the rocket after it leaves the Earths surface.Remember that the Moon is constantly circling the Earth.A rocket fired at the Moon and continuing in the direction in which it was fired would miss the Moon by a wide margin and perhaps continue to drift out into space until "captured" in another planets gravitational field.To reach the Moon, a rocket must be fired toward the point where the Moon will be when the rocket has traveled the required distance.This requires precise calculations of the speed and direction of the rocket and of the speed and direction of the Moon. For a rocket to arrive at a point where the Moons gravity will pull it the rest of the way, it must reach a speed called velocity of escape.This speed is about 25,000 miles per hour.At a speed less than this, a rocket will merely circle the Earth in an orbit and eventually fall back to the Earth.

This passage deals mainly with______.

A．the gravitational pull of the Earth and the Moon

B．the factors involved in firing a rocket into the outer-space

C．the gravitational fields of the Earth and the Moon

D．the speed and direction of a rocket traveling in the outer-space