Final answer:
A female rat that does not mate during her postpartum estrus typically starts cycling again within 11-14 days after giving birth.
Step-by-step explanation:
If a female rat does not mate during her postpartum estrus, she will return to cycling relatively quickly after giving birth. The correct answer to how long it takes a female rat to start cycling again after giving birth, if she does not mate during her postpartum estrus, is b) 11-14 days.
It is important to note that the estrus cycle in female rats is different than the menstrual cycle in humans. Female rats have a polyestrous cycle, meaning they go through multiple cycles throughout the year. While human cycles can be variable in length, a rat's postpartum estrus occurs just after giving birth, and if mating does not occur, they can quickly return to their regular cycle.