Final answer:
The gland with a honeycomb appearance due to highly folded mucosa is the gallbladder, which is characterized by rugae in its mucosa and concentrates bile by absorbing water and ions.
Step-by-step explanation:
The gland with highly folded mucosa giving the lumen a honeycomb look is the gallbladder. The simple columnar epithelium of the gallbladder mucosa is organized into rugae, similar to those in the stomach, which when contracted, contribute to the release of concentrated bile into the cystic duct and then into the bile duct. The gallbladder's mucosa is responsible for absorbing water and ions from bile, concentrating it significantly.