The correct option is C b and d are isotones
Nuclei with same number of protons but different number of neutrons are called Isotopes.
Nuclei with same number of neutrons but different number of protons are called Isotones.
Nuclei with same mass number are called Isobars.
ElementNeutron no.Proton no.Mass no.12C661214C861414N771416O8816
12C and 14C have same Proton number but different Neutron number. So, they are isotopes
14N and 14C have same mass number. So, they are isobars.
14C and 16O have same number of neutrons. So, they are isotones.