In order to recreate the process of energy production that takes place in the Sun, scientists use

1. hydrogen gas and add heat and pressure.
2. helium gas and remove heat and pressure.
3. hydrogen gas, add heat, and remove pressure.
4. helium gas, remove heat, and add pressure.

The correct answer is 1. hydrogen gas and add heat and pressure.

Explanation:

Nuclear fusion is the source of energy of the sun. During nuclear fusion because of the high temperature and pressure in the sun's core the nucleus of two hydrogen gets fused and form helium and the radiant energy is then released which comes to earth.

Therefore scientist are using this natural phenomenon so they are using hydrogen gas and addition heat and temperature so that they can recreate the process of energy production which takes place in the sun. So the correct answer is 1.

not only is it colder, it also becomes darker, less salty, and more dense.