Correct Option: B. Insulin Detailed Explanation:

1. Understanding Blood Glucose Regulation:
2. Blood glucose levels are crucial for maintaining energy homeostasis in the body. The body needs to keep these levels within a narrow range to ensure that cells have enough energy to function properly.
3. The pancreas plays a key role in regulating blood glucose levels through the secretion of hormones, primarily insulin and glucagon.
4. Role of Insulin:
5. Insulin is a hormone produced by the beta cells of the pancreas. Its primary function is to lower blood glucose levels.
6. When blood glucose levels rise after eating (especially carbohydrates), the pancreas releases insulin into the bloodstream.
7. Insulin facilitates the uptake of glucose by cells, particularly muscle and fat cells, allowing them to use glucose for energy or store it as glycogen for later use.
8. Insulin also inhibits the production of glucose by the liver, further helping to lower blood glucose levels.
9. Why Insulin is the Correct Answer:
10. Insulin directly promotes the uptake of glucose into cells, making it the primary hormone responsible for regulating blood glucose levels.
11. Without sufficient insulin, glucose remains in the bloodstream, leading to high blood sugar levels, a condition known as hyperglycemia.

Why the Other Options are Incorrect: A. Cortisol: - Cortisol is a steroid hormone produced by the adrenal glands and is often referred to as the "stress hormone." - While cortisol does play a role in glucose metabolism, its primary function is to increase blood glucose levels by promoting gluconeogenesis (the production of glucose from non-carbohydrate sources) and reducing the uptake of glucose by cells. Therefore, it does not promote glucose uptake but rather increases blood sugar levels. C. Glucagon: - Glucagon is another hormone produced by the pancreas, specifically by the alpha cells. - Its primary role is to raise blood glucose levels when they are too low (hypoglycemia). It does this by stimulating the liver to convert stored glycogen into glucose and release it into the bloodstream. - Thus, glucagon works in opposition to insulin, making it incorrect as the hormone responsible for promoting glucose uptake into cells. D. Adrenaline: - Adrenaline (or epinephrine) is produced by the adrenal glands and is involved in the body's "fight or flight" response. - It increases blood glucose levels by promoting glycogenolysis (the breakdown of glycogen to glucose) and inhibiting insulin secretion. Like cortisol and glucagon, it does not promote glucose uptake into cells. Summary of Key Points:

• Insulin is the primary hormone that regulates blood glucose levels by promoting glucose uptake into cells.
• Cortisol, glucagon, and adrenaline all work to increase blood glucose levels rather than decrease them.
• Understanding the roles of these hormones is crucial for grasping how the body maintains energy balance and responds to changes in blood sugar levels.
• Insulin's action is vital for preventing hyperglycemia and ensuring that cells receive the glucose they need for energy.