<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 example that does not exhibit sexual selection is:
D. male elephant seals fighting over territory and potential female mates
The competition for territory is also one that helps the elephant seals survive. This is because a seal with a larger territory is likely to have access to a greater amount of resources, ensuring its survival.
The variety of all life forms on Earth.
