Stars obtain their energy from:

1. Nuclear fusion
2. Gravitational contraction
3. Chemical reaction
4. Nuclear fission

Select your answer from the codes given below:
Codes:

Explanation

The answer is: (1) 1 and 2

1) Nuclear fusion is the dominant process where nuclei of light elements, like hydrogen, combine to form heavier elements, releasing tremendous amounts of energy.

2) As a star forms, its own gravity pulls its matter inwards. This contraction generates heat and pressure, contributing to initiating and sustaining nuclear fusion.

3) Chemical reactions play a negligible role in star energy production compared to nuclear fusion.

4) Nuclear fission, the splitting of heavy nuclei, is not a major energy source in stars. It's more relevant in specific stellar events like supernovae or certain types of nuclear reactors.