Question

阅读理解 　　A wind tunnel is a device used for testing airplanes or plane models． 　　In a wind tunnel air is blown over an airplane or a model placed in a test section．Wind tunnel test sections are different in size depending on airflow speed requirements．Some low-speed tunnels have test sections large enough for a complete small airplane．In the very high-speed tunnels used for space testing, however, the model may be as small as a pencil． 　　There are two methods of feeding air to the test section．In the continuous flow tunnel air-flow is produced by electric fans．It is forced through the tunnel to the test section, then through another tunnel section back to the starting point for refuse． 　　The other method involves storing high-pressure air in a box, sending it out by a control device to pass through the tunnel and test section into another box．This type of system is generally used for a very short period of high-speed airflow． 　　Wind tunnels are usually used to test airplanes before they are flown．Problems in an airplane can be found when it meets the high-speed airflow in the tunnels．For instance, if the wings are built so that they would weaken at high speeds, this fact can be discovered in the tunnel, saving many lives and millions of dollars． 　　In a wild tunnel scientists also find out how different planes will act at different speeds．They find out such things as how smoothly an airplane is flown, how slowly a plane can fly before it starts to drop, and how fast it can climb． (1) Some wind tunnel sections are larger than others because ________． [　　] A． they are used for larger planes B． stronger wind can be produced in them C． they are built to meet higher requirements D． the wind used in them flows at a lower speed (2) What does the underlined part “this fact” refer to? [　　] A． The wings are not good enough． B． It costs a lot to test a plane． C． Some problems are found about the plane． D． Many people will die in a plane accident． (3) A wind tunnel can be used to find out ________． [　　] A． how fast a plane can rise B． how smooth a plane’s surfaces are C． if a plane can land in windy and rainy weather D． if a plane will drop when flying at a low height (4) The writer wrote the passage mainly to explain ________． [　　] A． how a plane is built B． how a plane can be tested C． the relation between the wind and speed D． it is difficult to test a plane

Answer 1

答案：1．D;2．A;3．A;4．B;
解析：

(1)	根据第二段第二、三句可知答案。
(2)	这里的this fact是指上文所说的。if the wings are built so that they would weaken at high speeds(如果机翼造得不那么好，遇到强气流就会弱化)。
(3)	文章最后一句给出了答案。
(4)	本文介绍一种检验飞机的装置——风道。飞机起飞前经过检验，可检查出飞机可能存在的问题，从而保证飞行的安全。文章首句是全文的主题句，下文都是围绕“怎样用风道来检验飞机”这一主题来展开的。