Answer:
D. Work an entry level position at a veterinary clinic
Step-by-step explanation:
To become a veterinarian, get into vet school, get a job as a veterinarian, etc. You need experience. In this case, if he works a position at a veterinary clinic, he would be getting experience of what its like. He could be doing a job such as simply taking the dogs for a walk, and that would still be considered experience! So the answer would be D.
I also relate to this question a bit since I plan on going to vet school after I graduate. Hope this helps :)