Final answer:
A cow would have a reticular groove, a feature of the ruminant digestive system that is not found in monkeys, eagles, or kangaroos.
Step-by-step explanation:
The animal that would have a reticular groove among the given options is a. Cow. The reticular groove is a feature of the ruminant digestive system, found in animals like cows, goats, and deer. This structure helps in directing milk directly to the omasum when they are young and nursing, bypassing the rumen to prevent fermentation of the milk. It is not found in the other listed animals: monkeys, eagles, or kangaroos, as they do not have the same ruminating digestive system.