D, light can travel in the air or a vacuum and the speed is constant whether the light source is stationary or moving.
<span>m, M\</span>
<span>is mass symbol </span>
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<u>Answer</u>:
The mass of a star can be determined by studying binary star systems.
<u>Explanation</u>:
In this system it consists of two stars, revolving round the same bary-centre. The systems having two or may say more than two are called as the multiple star system. This zone is also a habitable zone, here the water exists in the liquid form. We could have sometime seen the two stars together. They are also very capable of strengthening the terrestrial planets inside the stable orbital ranges. They have generally two orbits like P-type as well as circumbinary.
The answer is c. Vibrates on one spot
Yes, the planet obeys the Kepler's Second Law. It is because it moves at equal time of one month at the same distance.
