Islets of Langerhans are present in

The correct answer is D ‘Pancreas’.

A: Brain- The brain is a complex organ that regulates our body's thought, memory, emotion, touch, motor skills, vision, breathing, temperature, hunger, and every other process. The central nervous system, or CNS, is made up of the brain and the spinal cord that extends from it.

B: Stomach- The stomach is a muscular organ located on the upper left side of the body. Food enters the stomach from the esophagus. When food reaches the esophagus's end, it enters the stomach via a muscular valve known as the lower esophageal sphincter. The stomach secretes acids and enzymes that aid in the digestion of food.

C: Ovary- The ovary is a ductless reproductive gland that produces female reproductive cells. Females have two ovaries, which are held in place by a membrane beside the uterus on each side of the lower abdomen. The ovary is required for reproduction because it produces female reproductive cells or ova.

D: Pancreas- The pancreas contains Langerhans Islets. They are part of the pancreas' endocrine system. They are made up of three types of cells:

Alpha cells: These cells account for approximately 25% of total cells and secrete the 'Glucagon' hormone.

Beta cells: These cells account for more than 60% of total cells and secrete the hormone insulin.

Delta cells: These cells account for about 10% of all cells and secrete the hormone 'Somatostatin.'

Hence, the correct answer is D, Pancreas.