航海英語天文航海單項選擇題每日一練(2019.01.25)

來源：考試資料網(wǎng)

1 In the horizon system of coordinates what is equivalent to the equator on the Earth?（）.

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2 A marine sextant has the index arm set at zero and the reflected image of the horizon forms a continuous line with the actual image. When the sextant is rotated about the line of sight the images separate. The sextant has（）.

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3 Right ascension is primarily used by the navigator for（）.

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4 A large group of stars revolving around a center is known as a（）.

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5 Mars will not be visible（）.

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