Final answer:
The ground state electron configuration of Y^3+ is Kr 5s^2 4d^4.
Step-by-step explanation:
The ground state electron configuration of Y^3+ can be determined by removing three electrons from the neutral atom, Y. The electron configuration of Y is [Kr]5s^2 4d^1, so removing three electrons gives us [Kr]5s^2 4d^4. Therefore, the correct answer is c) Kr 5s^2 4d^4.