Isotopes are variations of elements that have different numbers of neutrons in their nucleus, therefore they have different masses. The number of protons in the nucleus does not change.
On the other hand, to represent an isotope we have the following general form:
If we compare the options we must take into account that the Z value, it means the number of protons does not change. So, the two options that conserves the same number of protons are I and IV.
Answer: d. I and IV