What is the defining characteristic of a main sequence star? o it is fusing hydrogen into helium in its core. o it is fusing helium into carbon in its core. o there are no longer any fusion reactions in its core.. o it is yellow.

Option (1)

Explanation: Main sequence stars refers to those stars that are formed due to the fusion of hydrogen atoms in order to form helium its core. This are initially comprised of dust, gases and interstellar particles. Example of main sequence star are T Tauri and the sun.

The extreme pressure that is generated due to its increasing temperature balances the gravitational force that helps in holding the star.

Thus, the correct answer is option (1).

7.03-1.70=5.33 and 6.80+5.09=11.89 and 5.5-3.01=2.49

a is the answer i believe.