Which is least effective for artificial transmutation?

If $_{92}U^{235}$ nucleus absorbs a neutron and disintegrates into $_{54}Xe^{139}$,$_{38}Sr^{94}$ and $X$,then what will be the product $X$?

In the nuclear reaction $_7N^{14} + _2He^4 \to _ZX^A + _1H^1$,the product nucleus $_ZX^A$ formed is:

The $_6C^{14}$ in the upper atmosphere is generated by which of the following nuclear reactions?

In the nuclear transmutation $_4^9 Be + X \longrightarrow _4^8 Be + Y$,the pair $(X, Y)$ is (are):

$_{13}Al^{28}$ when radiated by a suitable projectile gives $_{15}P^{31}$ and a neutron. The projectile used is: