Which of the following pairs is called isotones?

$A$ reaction between a proton and $_8^{18}O$ that produces $_9^{18}F$ must also liberate:

$STATEMENT-1$: The plot of atomic number ($y$-axis) versus number of neutrons ($x$-axis) for stable nuclei shows a curvature towards the $x$-axis from the line of $45^{\circ}$ slope as the atomic number is increased.
$STATEMENT-2$: Proton-proton electrostatic repulsions begin to overcome attractive nuclear forces in heavier nuclides,requiring more neutrons to maintain stability.

Out of gravitational,electromagnetic,Van der Waals,electrostatic,and nuclear forces,which two are able to provide an attractive force between two neutrons?

Match the following fundamental forces of nature with their relative strength:

List-$I$	List-$II$
$(A)$ Strong nuclear force	$(i)$ $10^{-2}$
$(B)$ Weak nuclear force	(ii) $1$
$(C)$ Electromagnetic force	(iii) $10^{-39}$
$(D)$ Gravitational force	(iv) $10^{-13}$

Which of the following is true for a sample of $U^{235}$ and $U^{238}$ isotopes?