Which of the following is considered a vestigial organ?

The appendix is considered a vestigial organ because it is a remnant of a larger cecum that is present in the digestive systems of many herbivorous ancestors. Over time, as human diets have evolved to become less reliant on the fermentation of cellulose found in plant matter, the appendix has lost its original function in digestion and has become less essential for survival. While it may still play a role in the immune system and in maintaining gut flora, it is not critical for digestive processes, which is the reason it is classified as vestigial.

In contrast, the other options serve important functions in the human body: the cecum is involved in the digestive process, the stomach plays a key role in breaking down food, and the pancreas produces enzymes critical for digestion and hormones such as insulin. Therefore, the appendix stands out as a structure that has diminished in importance through evolution, which supports its classification as a vestigial organ.