An echo is a reflected(反射)sound．Stand in a very large, empty hall with nothing on the walls．Then shout．The sounds you make will hit the walls and come back to you．The walls reflect the sounds．These reflected sounds are called “echoes”．
We can use reflected sound to make sound travel farther．Hold a watch about fifty centimeters from your ear．You cannot hear it．The sound of the watch travels a short way in all directions．It does not travel as far as your ear．You can make it travel to your ear by using a roll of cardboard(纸板筒)．
Make the roll of cardboard about fifty centimeters long．Put one end over your ear and hold the watch at the other．Now you can hear the watch because the sound has not gone in all directions．It is reflected down the roll to your ear．
A megaphone(喇叭筒)works in the same way．It makes sound travel farther．It reflects the sound into a beam which can travel a long way．In the ship, the sailor uses the megaphone to make his voice travel．Without the megaphone, his voice cannot travel far．
We use reflected sound in many ways．We use it to measure the depth of the sea, for example．Among the animals, bats and whales use reflected sound to tell them where they are and what things are near them．
(1)
What is called “echo”?
[ ]
A．
Very loud voices．
B．
Very loud voices that are made by man．
C．
Very loud voices that are made by animals．
D．
The sound that is made by man or animals comes back from some place．
(2)
Which is the right order of hearing our echo in a very large, empty hall?
a．We hear the reflected sound
b．The sound returns to us
c．The sound hits the walls
d．We make a sound
[ ]
A．
c, b, a, d
B．
c, a, b, d
C．
d, c, b, a
D．
d, b, c, a
(3)
From the text we learn that ________．
[ ]
A．
reflected sound is useful only to blind people
B．
people haven't made use of reflected sound yet
C．
bats use reflected sound to fly and get food
D．
whales don't use reflected sound as they live in the sea
(4)
If you haven't got a megaphone, ________ will help you to make your voice travel farther．
How much sleep do we need? The answers are different. Some people need only three hours of sleep a night. Others need ten hours of sleep a night. Most Amexicans sleep for an average of seven to eight hours a night. After age fifty, the average sleep hours go down to 6.5 hours a night.
Most people will have a bad night when they can't fall asleep. About one in three Americans has a problem with sleep. Many of these people cannot fall asleep. The name of this problem is called insomnia(失眠症).
This is not a new problem. Many famous people in history had insomnia .Some of these people had their own ways to sleep well. Benjamin Franklin(本杰明·富兰克林), the famous inventor, had four beds.He moved from one to another to fall asleep. King Louis XIV (国王路易十四) of France had 413 beds and hoped to fall asleep in one of them. Mark Twain, the famous writer, had a different way: he hy on his side(侧卧) across the end of the bed!
(1)
Most Americans usually sleep for about _________ hours a night.
A. 3 B. 5～6 C. 10 D. 7～8
[ ]
(2)
As people grow older,they need __________ at night.
A. less sleeping time
B. more sleeping time
C. the same amount of sleeping time
D. a fixed time to sleep
[ ]
(3)
If there are 100 million people in the US hav-ing a problem with sleep,what's the popula-tion of it? About _______.
A. 200 million B. 300 million C. 600 million D. 900 million
[ ]
(4)
Franklin tried to go to sleep by __________.
A. moving from one to another of his 413 beds B. moving from one to another of his 4 beds
C. inventing a bed for himself D. lying on his side across the end of the bed
[ ]
(5)
It's not mentioned in the passage,but we know that Mark Twain was ___________.
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