There are some objects in the sky that move so quickly that sometimes you only see them out of the corner of your eye. These are some ofthe hugenumber of bits of rock and dust that are floating around in space,calledmeteoroids. Normally, we cannotsee them at all, but if they travel too close to the Earth, they get caught bythe pull of the Earth, and beginto fall towards us. They fall faster andfaster, until they hit ouratmosphere (大氣層), by which timethey are going so fast that they begin to burn up, and all that you see is aflash of light that moves very quickly across the sky and disappears. Theseshooting stars, or meteors as they are properly called, are quite common, andsometimes you may see several in a night.

　　Most meteoroids are very small bits indeed, and they bum uplong before they get to the Earth. However, a very few do manage to get all theway through the atmosphere, and actually fall to the ground. Usually they donot do much damage, although this is not always the case. Meteoroids that actuallymanage to reach the Earth are called meteorites. Most countries have places where meteoriteshave struck theEarth. Some of these places are very large indeed and aretourist attractions.

　　67. Why do some objects from outer space fall to theground?

　　[A] They are too big.

　　[B] They arc hit by huge rocks.

　　[C] They move too fast.

　　[D] They are pulled by the Earth.

　　68.What do we know about meteors from the text?

　　[A] They become a star in the sky.

　　[B] They are too small to be seen.

　　[C] They disappear very quickly.

　　[D] They do damage to the Earth.

　　69. What happens to most meteoroids coming into theatmosphere?

　　[A] They burn up.

　　[B] They fall to earth.

　　[C] They explode.

　　[D] The float in the air.

　　70. The word “meteorites” (Line 1, Para.3) refers to piecesof rock

　　that _____.

　　[A] move fast in outer space

　　[B] have been found at a tourist centre

　　[C] flash through space at a high speed

　　[D] have fallen onto the Earth from space

　　【答案及解析】

　　67.D 細節(jié)題。由原文第一段中的“Normally, we cannot see them at all, but if theytravel too close to the Earth, they get caught by the pull of the Earth, andbegin to fall towards us.”可知，有一些物體，通常我們根本看不見它們，但是如果它們離地球太近，受地球引力作用，它們就會落向地球。因此 D 項“受地球引力作用”正確。

　　68.C 細節(jié)題。由原文第一段中的“they are going so fast that they begin to burnup, and all that you see is a flash of light that moves very quickly across thesky and disappears.”可知，它們下落的速度如此之快以至于它們開始燃燒，你只能看到一道光迅速劃過天際，然后消失不見。即流星會很快消失，因此 C 項正確。

　　69.A 推理題。由原文第一段中的“They fall faster and faster, until they hit ouratmosphere, by which time they are going so fast that they begin to burn up”可知，它們下落的速度越來越快，直到它們到達大氣層，這時，它們的速度如此之快以至于開始燃燒。即流星體到達大氣層時會燃燒。因此 A 項正確。

　　70.D 詞義理解題。由原文第三段中的“Meteoroids that actually manage to reach the Earthare called meteorites.”可知，最后成功到達地面的流星體被稱為隕石。因此 D 項正確。