The is responsible for regurgitation of food during rumination.

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.  

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

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