Answer
Atom D is the isotope of atom A.
Work Step by Step
Steps: Isotopes are atoms that have the same number of protons but they have different number of neutrons. In other words isotopes are the atoms that have the same atomic number, but different mass number.
We see that only atom D has the same number of protons with atom A, ( 32 protons) but they have different number of neutrons ( 39 neutrons for atom A and 38 neutrons for atom D).
Therefore atom D is isotope of atom A.