Question

阅读理解 　　Under proper conditions, sound waves are reflected from a hillside or other such obstruction 　　(障碍物)．Sound travels at a speed of about one-fifth of a mile per second．If the hill is eleven hundred feet away, it takes two seconds for the sound to travel to the hill and back．Thus by measuring the time between a sound and its reflection the echo(回声), you can calculate(计算)the distance to an obstruction． 　　During World WarⅡ the British made a practical use of this rule to discover German planes on their way to bomb(轰炸)London long before the enemy was near the object．They used radio waves instead of sound waves, since radio waves can pass through fog and clouds．The outnumbered Royal Air Force(RAF)(皇家空军)always seemed to be lying in wait at the right time and the puzzled Germans never to be surprised．It was radio echoes more than anything else that won the Battle of Britain． 　　Since the radio waves were used to tell the direction in which to send the RAF planes and the distance to send them［their range(距离范围)of flight, in other words］, the device(装置)was called radio directing and ranging, and from the first letters the word radar(雷达)was formed． (1) Sound waves reflected from a hill can be used to calculate the _________． [　　] A． speed of sound B． time between a sound and its echo C． height of the hill D． distance to the hill (2) The British used radio waves because they _________． [　　] A． were more exact than sound waves B． could not be discovered C． could pass through fog and clouds D． were easier to use than sound waves (3) Practical use of radio waves brought about _________． [　　] A． new machines for planes B． a radio directing and ranging device C． new radio sets for RAF bombers D． a discovering device (4) Radar allowed British to be able to _________． [　　] A． discover German planes on their way to London B． direct the outnumbered RAF planes effectively C． kill German bomber pilots D． both A and B (5) The author of this passage mainly wanted to explain _________． [　　] A． exactly how radar worked B． why the British used radio waves in their device C． how radar(word and device)came into being D． how radar helped the British win the battle

Answer 1

答案：1．D;2．C;3．B;4．D;5．C;
解析：

(1)	从第一段可判断是用来测算山的距离。而A、B两项是人们已知的信息；C项文不对题。
(2)	从第二段第二句可找到答案。
(3)	无线电波的实际运用导致了“无线电定向测距仪”这个装置的产生。
(4)	第二段第一句和第三段的前半句便是答案。
(5)	短文的句末是本题答案所在，即“雷达”这个词和装置是如何产生的。