Question

阅读下列短文，从所给的四个选项中，选出最佳答案。

　　Why does pouring hot water over a tight jar lid will loosen it?

　　Hot water makes the metal of the jar expand; this makes the cover　　 loose.

　　Most objects expand when heated because they are made of molecules　　 that are in constant motion. Heat makes molecules(分子)move faster.　　 The hotter the molecules become the faster they move and the more　　 space they need.

　　This explains why we hear a click(卡嗒卡)as we travel by train, or　　 a gentle thump(撞击)as we drive on a concrete(混凝土)highway. The　　 clicks and thumps tell us that we are passing over expansion joints put　　 in to allow room for the metal rail and the concrete to expand. Those　　 joints prevent the rails and the road from buckling(弯曲)as they　　 expand under the hot sun. Like the molecules of the jar lid, the　　 molecules of these materials need more space when they are hot.

(1)  Pouring hot water over a jar lid will _______.

[    ]

A. loosen it   

B. make the jar expand 

C. not affect the lid itself   

D. tighten it 

(2)  This happens because the hot water _______.

[    ]

A. causes the jar to grow smaller

B. heats whatever is inside the jar

C. makes the lid slightly larger

D. all of the above

(3)  An object is made up of molecules that move ____.

[    ]

A. all the time　　 

B. for some time

C. if the object becomes very hot

D. whenever hot water is poured over it

(4)  Objects expand when they are hot because hot molecules ____.

[    ]

A. move faster

B. move slowly

C. take up more room

D. both A and C

(5)  From this selection we can tell that the molecules in a road_____.

[    ]

A. are like no other molecules 

B. are not much like those in a jar lid

C. behave(行动)like the molecules in rails, lids and other  objects

D. will not expand even in the hot sun

Answer 1

答案：A;C;A;D;C