(a) Both are equally stable
(b)NH4+ ion is less stable then CH3+ ion bcz is the former +ve charge is present on the more electronegative element
(C) NH4+ ion is more stable then CH3+ ion bcz is the former is an inorganic ion, while the latter is an organic ion
(D) NH4+ ion is more stable bcz here N has complete octet of electron, while H has duet
