The atomic number of an element ' M ' is 26 . How many electrons are present in the M-shell of the element in its ${\mathbf{M}}^{3+}$ state?

$\mathrm{M}(\mathrm{Z}=26):1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{2}3{\mathrm{d}}^6$
${\mathrm{M}}^{3+}:1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^5$
M-shell denotes the third shell, where n=3. 

In M⁺³ ion , the third shell has 13 electrons.

Hence , the correct option is ( D).