Consider the species ${\mathrm{CH}}_4,{\mathrm{NH}}_4^{+}$and ${\mathrm{BH}}_4^{-}$. Choose the correct option with respect to the there species.

They are isoelectronic and only two have tetrahedral structures.

Only two are isoelectronic and all have tetrahedral structures.

They are isoelectronic and all have tetrahedral structures.

Only two are isoelectronic and only two have tetrahedral structures.