Each culture has its own form of acceptable greeting behavior, usually based on the level of formality found within the society. The rules of social distance etiquette (礼节) vary by culture. Africans, for ex- ample, are far less (47) in their greetings than Europeans. Expect a warm physical greeting, an ex- tended handshake or a hand on the shoulder in most African cultures. Also expect to be asked how your trip was and how your family is doing. The tradition of long greetings stems (48) the time when Africans once walked miles to visit neighboring villages on social calls. The arrival and a gushing (说话滔滔不绝的) greeting was considered the (49) a villager could do for a traveler. Don’t be impatient with such a long drawn-out(冗长乏味的) (50) and don’t burry things along. Rather, get into the spirit and appreciate that the person you came to see is prepared to take the time to sincerely (51) about your welfare.
In Argentina, greetings are usually effusive(过分热情的) with plenty of hugging and (52) , not unlike the French faire la bise ( kiss on both cheeks). This is even the case in business meetings, unless they are of a highly formal nature. In Argentina, men kiss women, women kiss women, (53) men do not kiss men. By contrast the Chinese way of greeting shuns(回避) the physical. It is (54) a nod or a slight bow. However, when dealing with individuals from cultures where more direct physical contact is the norm, e.g. , a handshake, the Chinese will (55) and shake hands. Don’t interpret a soft hand- shake or lack of eye contact as a sign of weakness or lack of aggression. It simply means that your Chinese colleague is, not overly (56) to physical contact when greeting a stranger.
A. from B. structured
C. but D. generally
E. expedition F. inquire
G. adapt H. kissing
I. investigate J. touching
K. used L. least
M. exchange N. chance
O. involved

A. comprehensive education and un-streamed classes
B. grouping of children into different classes
C. sending the duller children out to work at an early age
D. taking "disadvantaged" children away from their home environment

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’s a point somewhere along that line, nearer to the moon than to the earth, at which the gravitational 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 moon’s 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 earth’s gravitational field reaches far closer to the moon than does the moon’s to 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 earth under the earth’s 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 earth’s 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 planet’s gravitational field. To reach the moon, a rocket must be tired 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 moon’s gravity will pull it the rest of the way, it must reach a speed called the velocity of escape. This speed is about 25, 000 m/les (about 40,200 kilometers) 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.