Final answer:
The gizzard in avian species is referred to as the ventriculus and is a muscular organ that aids in the grinding of food, helping it to be digested more quickly due to the absence of teeth in birds.
So, the correct answer is C.
Step-by-step explanation:
In avian species, the gizzard is referred to as the ventriculus. The avian digestive system is specialized to compensate for the absence of teeth. Birds use their beaks to acquire food, and their high metabolic rates from flying necessitate efficient food processing.
The two main components in their digestive system are the proventriculus, where digestive juices begin the breakdown of food, and the gizzard, which mechanically grinds the food often with the aid of ingested stones or grit. This grinding process allows for quicker digestion. The gizzard is well developed in birds that eat grains and performs a vital role in their digestion.
Additionally, the elimination of wastes from the bird's body is through an opening called the cloaca, which serves for the excretory, digestive and reproductive systems. So, the correct answer is C) Ventriculus.