The correct answer is the reticulum.
Rumination refers to the procedure of rechewing the cud, which facilitates the complete dissociation of the cellulose-rich plant matter. Ruminants refer to a category of herbivorous mammals, they are hoofed, toed mammals that consume food in bulk and digest afterward. For example, sheep, cow, goat, camel, giraffes, and others.
The main characteristic of ruminant mammals is their chambered stomach. The ruminant stomach has four chambers, that is, the reticulum, rumen, abomasum, and omasum. The reticulum refers to the second chamber of the ruminant stomach. It exhibits regular contractions that precede the biphasic ruminal contraction for digestion of food particles.