阅读下面短文.然后从下列各题所给的四个选项中选出一个最佳答案. The first telegraph cable was laid under the sea

阅读下面短文，然后从下列各题所给的四个选项中选出一个最佳答案。

The first telegraph cable was laid under the sea between England and France in 1850．Cables are much 1 and heavier than telegraph wires．There are a number of reasons for this：one reason is that the salt water of the sea harms 2 telegraph wires, and so they have to be 3, another is that, because electricity 4 easily through water, wires have to be 5 to prevent electric signals which are passing through them 6 escaping and getting lost in the sea; a third reason is that cables have to be very strong 7 they will break while they are being 8 along the bottom of the sea from a ship sailing on the surface．

The 9 cables that men tried to lay 10 England and America broke and were 11 during storms．At last, after nine years of hard work, the two English-speaking nations of Britain and America were 12 in 1866 by the electric telegraph under the sea．

Later, all the different 13 of the world were joind up by a 14 of cables．It is 15 easy to send a message by cables as it is to 16 an ordinary telegram, and it takes no longer for a message to 17 half way round the world than from one town to the 18．Every hour of the day and night 19 are being flashed under the ocean to and 20 every country in the world．

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