Dr Smith, a Veterinarian, Has Hired Carlos as an Assistant

Dr. Smith, a veterinarian, has hired Carlos as an assistant. On Carlos's first day at work, Dr. Smith shows him the technique of holding a cat for vaccination. First, Dr. Smith describes the technique and then he practically shows the process of vaccination. Later he asks Carlos to hold the cat and corrects the mistakes Carlos makes while holding the cat. This is an example of:

A) cross-training.
B) virtual training.
C) simulation training.
D) on-the-job training.