Concept:Insulin is a hormone that lowers blood glucose, and it is secreted by the endocrine part of the pancreas.
Explanation:The pancreas contains clusters of endocrine cells called the islets of Langerhans.
Inside these islets,
β cells detect high blood sugar levels.
These
β cells synthesize and release insulin into the bloodstream.
Insulin then helps cells absorb glucose and lowers blood sugar concentration.
The other options are incorrect because the spleen is not an endocrine gland, the adrenal gland secretes adrenaline and cortisol, and the thyroid gland secretes thyroxine and calcitonin.
Therefore, the organ responsible for insulin production is the pancreas.
Answer:D. Pancreas