Inside the sun _______ reactions take place at high temperature and enormous pressure. Fill in the blanks
(A) Nuclear fusion
(B) Nuclear fission
(C) Catalyze
(D) None of these

Hint:- Nuclear fusion is the reaction where two lighter nuclei combine to form a heavier nucleus. And the nuclear fission is the breakage of heavy nuclei into lighter nuclei. The core of the sun has hydrogen which is a lighter nucleus.

Complete Step by step answer:
The core of the sun consists of hydrogen gas. This hydrogen nuclei undergoes nuclear fusion at high temperature and enormous pressure and forms helium atoms. This fusion is also known as proton- proton fusion. The hydrogen nucleus is called protons. And these protons combine to form helium atoms. The nuclear reaction will generate heat which makes the sun hot. And the energy is radiated from the sun.
Let’s see the process in detail.
The fusion of two protons will produce a positron and neutron. This positron and neutron pair is also called deuterium. When a third proton collides with this deuterium, the reaction will produce a helium-$3$ nucleus and a gamma ray. Those Gamma rays are the sunlight that comes from the sun. When two helium-$3$ nuclei fuse a helium- $4$ nucleus and two protons are produced.
Therefore, Inside the sun nuclear fusion reactions take place at high temperature and enormous pressure

The answer is option A.

Note: We have to note that only at the core of the Sun, the nuclear fusion will take part. The energy for the other regions is transferred from the core of the Sun.