The correct option is C in case of square planar shape two isomers on mono substitution will be possible which is not observed in CH4
CH4 has four identical C−H bonds and non-polar in nature. It would have been better if it were supposed to have square planar structure but it is assigned tetrahedral geometry. This is because in case of square planar shape two isomers on mono substitution will be possible which is not observed in CH4.It is a reason propose square planar geometry for CH4.For square planar arrangement for CH4, the four C−H bond pairs have to lie right angle to each other.