Pick out the unmatched pair from the following $:-$

According to classical physics,$10^{-15} \ m$ is the distance of closest approach $(d_c)$ for fusion to occur between two protons. $A$ more accurate quantum approach states that $d_c = \frac{\lambda_p}{\sqrt{2}}$,where $\lambda_p$ is the de Broglie wavelength of a proton when they were far apart. Using this quantum approach,find the equation for the temperature $(T_c)$ at the center of a star. [Given: $M_p$ is the mass of the proton,$k$ is the Boltzmann constant,$e$ is the elementary charge]

Nuclear fission and fusion can be explained on the basis of

What is nuclear fusion? Explain giving its nuclear equations and write down the definition of thermonuclear fusion.

In a nuclear fission process,a high mass nuclide $(A \approx 236)$ with binding energy $7.6 \ MeV/\text{nucleon}$ dissociates into two middle mass nuclides $(A \approx 118)$,each having a binding energy of $8.6 \ MeV/\text{nucleon}$. The energy released in the process is $MeV$.

In the given nuclear reaction
${ }_{4}^{9} Be+{ }_{2}^{4} He \rightarrow{ }_{6}^{12} C+X$
$X$ represents $\qquad$