What percentage of mass is converted into energy during nuclear fission?

$A$ nuclear reactor process is said to be critical when the value of the multiplication factor is .......

The binding energy of deuteron $_1^2H$ is $1.112 \, MeV$ per nucleon and an $\alpha$-particle $_2^4He$ has a binding energy of $7.047 \, MeV$ per nucleon. Then in the fusion reaction $_1^2H + _1^2H \to _2^4He + Q$,the energy $Q$ released is ........ $MeV$.

Choosing the correct option, complete the given nuclear fusion reaction that occurs in the sun.
${ }_1^3 H +{ }_1^3 H \rightarrow{ }_2^4 He +{ }_1^1 H +{ }_1^1 H +$ . . . . . . . (in $\text{ MeV}$)

The energy released per fission of a nucleus of ${}^{240}X$ is $200 \ MeV$. The energy released if all the atoms in $120 \ g$ of pure ${}^{240}X$ undergo fission is $........ \times 10^{25} \ MeV$. (Given $N_A = 6 \times 10^{23}$)

The process that mainly takes place in stars to produce energy is: