Final answer:
The breasts, which contain mammary glands, are responsible for milk production to feed an infant after childbirth, in a process known as lactation.
Step-by-step explanation:
The part of the female reproductive system responsible for producing milk after childbirth is c) Breasts. Although not directly involved in the reproductive process, the breasts contain mammary glands that produce milk to feed an infant. This milk production, known as lactation, occurs in response to the baby suckling at the breast. The milk drains from the mammary glands into ducts leading to the nipple, where it can be accessed by the nursing infant.