Light energy emitted by stars is due to

By which process is the energy released from the Sun?

To generate a power of $3.2 \text{ MW}$,the number of fissions of $^{235}\text{U}$ per minute is (Energy released per fission $= 200 \text{ MeV}$,$1 \text{ eV} = 1.6 \times 10^{-19} \text{ J}$)

Suppose a ${ }_{88}^{226} Ra$ nucleus at rest and in the ground state undergoes $\alpha$-decay to a ${ }_{86}^{222} Rn$ nucleus in its excited state. The kinetic energy of the emitted $\alpha$ particle is found to be $4.44 \text{ MeV}$. The ${ }_{86}^{222} Rn$ nucleus then goes to its ground state by $\gamma$-decay. The energy of the emitted $\gamma$-photon is . . . . . . . $\text{keV}$.
[Given: atomic mass of ${ }_{88}^{226} Ra = 226.005 \text{ u}$,atomic mass of ${ }_{86}^{222} Rn = 222.000 \text{ u}$,atomic mass of $\alpha$ particle $= 4.000 \text{ u}$,$1 \text{ u} = 931 \text{ MeV}/c^2$]

Which of the following statement$(s)$ is/are correct?

Energy in the sun is generated mainly by