Species X with mass number 37 contains 11.1% more neutrons as compared to electrons,  then what is the incorrect representation of element X ?

Since mass number is 37, option (c), (d) are not possible. Now according to option (a) and (b) no. of neutrons $=20;$no. of $e^{-}=\frac{20}{1.111}=18$. Hence, species is ${ }_{17}^{37}{\mathrm{Cl}}^{-}$.