Name the allotropes of tin present in nature.

Explain the following property of group 16 elements:

Allotropy

The nitrogen family elements have more ionisation enthalpy than oxygen family. The valence shell electronic configuration of bismuth is $\mathrm{X}$. $\mathrm{X}$ can be _____:

$\mathrm{A}. \mathrm{X}=\left[\mathrm{Xe}\right] 4{\mathrm{f}}^{14}5{\mathrm{d}}^{10}6{\mathrm{s}}^{2}6{\mathrm{p}}^3, \mathrm{B}. \mathrm{X}=\left[\mathrm{Xe}\right] 4{\mathrm{f}}^{14}5{\mathrm{d}}^{10}6{\mathrm{s}}^{2}6{\mathrm{p}}^2, \mathrm{C}. \mathrm{X}=\left[\mathrm{Xe}\right] 4{\mathrm{f}}^{14}5{\mathrm{d}}^{10}6{\mathrm{s}}^{1}6{\mathrm{p}}^3$

" Enter your answer as $\mathrm{A}, \mathrm{B}$ or $\mathrm{C}$."