The isotopes of an element contain :
(a) same number of neutrons but different number of protons
(b) same number of neutrons but different number of electrons
(c) different number of protons as well as different number of neutrons
(d) different number of neutrons but same number of protons
option (d)
Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons in each atom.