Concept:Ductless glands are endocrine glands that release hormones directly into the bloodstream, not through tubes or ducts.
Exocrine glands have ducts that carry their secretions to a surface or cavity.
Explanation:The adrenal and parathyroid glands are true ductless endocrine glands.
The pancreas also contains ductless islet cells that secrete insulin and glucagon into the blood.
The salivary gland, however, is an exocrine gland.
It releases saliva through a duct into the mouth.
Saliva contains the enzyme ptyalin, but it is discharged into the mouth, not directly into the blood.
Therefore, the salivary gland is the one that is not ductless among the options.
Answer:D. salivary