___________ is the process of collecting semen from a stallion and depositing that semen into the mare.

Artificial insemination is the correct choice because it specifically refers to the method of collecting semen from a stallion and then manually depositing that semen into a mare's reproductive tract. This technique allows for controlled breeding, often facilitating genetic selection and improving the chances of conception.

In contrast, natural breeding involves the stallion mounting the mare and breeding in a more traditional manner, without any human intervention in the semen collection or deposition. In vitro fertilization refers to the process where eggs are fertilized by sperm outside the mare's body, which is not relevant to the direct collection and deposition of semen. Embryo transfer involves the transfer of a fertilized embryo into a recipient mare, which comes into play after fertilization has already occurred. Therefore, the precise definition of artificial insemination aligns perfectly with the process described in the question.