Final answer:
The statement that a simple gland has an unbranched duct is true for the classification of glandular epithelium. Unicellular glands are considered simple, and glands with ducts can be either tubular or acinar, while combinations of these structures form tubuloalveolar compound glands.
Step-by-step explanation:
The classification of glandular epithelium is based on several factors, including the structure of the glands and the shape of their ducts. Among the statements provided, the correct one is: a simple gland is one that has an unbranched duct. Simple glands have a single, unbranching duct, whereas compound glands have branched ducts. Unicellular glands such as goblet cells are indeed simple glands because they don't have ducts and release their secretions directly to the surface. Glands with ducts can be either tubular or acinar depending on the shape of their secretory parts, with the exocrine portion of the pancreas being an example of an acinar gland. The combination of tubular and acinar structures forms tubuloalveolar (tubuloacinar) compound glands.