题目内容
阅读理解
The first telegraph cable (电缆) was laid under the sea between England and France in 1850. Cables are very much thicker and heavier than telegraph wires. There are a number of reasons for this. One reason is that the salt water of the sea harms ordinary telegraph wires, and so they have to be protected. Another is that, because electricity passes easily through water, wires have to be covered to prevent electric signals which are passing through them from escaping and getting lost in the sea. A third reason is that cables have to be very strong or they will break while they are being laid on the bottom of the sea from a ship sailing on the surface.
(1) People put the first cable on the bottom of the sea between England and France ________ .
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A.about half a century ago
B.in the Middle Ages
C.in the middle of the 18th century
D.in the middle of the 19th century
(2) Ordinary telegraph wires have to be protected in the sea because________ .
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A.they are not thick enough
B.they are not strong enough
C.salt water of the sea is very harmful to them
D.they are made of metal
(3) Electricity signals easily escape and get lost________ .
[ ]
(4) Cables under the sea have to be made very strong, otherwise ________ .
[ ]
A.the sailing ship may break them
B.fishes may bite them
C.they may rise above the water
D.they may break when being laid down into the sea from a ship
(5) The main idea of the passage is________ .
[ ]
A.Electricity passes easily through water
B.It is difficult to lay cables into the sea
C.Ordinary telegraph wires can't be kept long under the sea
D.The reasons why telegraph cables are much thicker and heavier than telegraph wires
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