In 2012， Jiaolong manned submersible made a 7000 meter sea trial。 Before that， only the US， France and Russia had manned deep submarines in the world。（ ）
In 2012， Jiaolong manned submersible made a 7000 meter sea trial。 Before that， only the US， France and Russia had manned deep submarines in the world。（ ）
The last sentence means that a knowledge of fish sounds can help man to （）. A: avoid confusion in fishing activity B: avoid unneeded effort in fish sound studies C: detect enemy submarines D: pick up new sounds
The last sentence means that a knowledge of fish sounds can help man to （）. A: avoid confusion in fishing activity B: avoid unneeded effort in fish sound studies C: detect enemy submarines D: pick up new sounds
Which of the following is NOT true of a laser system A: It is able to make its way through water. B: It is able to communicate with submarines at work. C: Its beam reaches a submerged submarine with the help of an antenna. D: It is able to carry more data than low frequency waves.
Which of the following is NOT true of a laser system A: It is able to make its way through water. B: It is able to communicate with submarines at work. C: Its beam reaches a submerged submarine with the help of an antenna. D: It is able to carry more data than low frequency waves.
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