Question

plz guys get me a perfect answers for these questions​

Answer 1

Explanation:

Sonar (sound navigation ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels. The term sonar is also used for the equipment used to generate and receive the sound.

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Answer 2

Petroleum is called black gold because when crude oil is extracted from the land it is black in color.Crude oil is jet black before purification but after purification, it turns golden in color; therefore, it's tagged as Gold.