Insulin is a hormone produced by the pancreas that plays a crucial role in regulating blood sugar levels in the body. It helps control the level of sugar (glucose) in the bloodstream. When we eat carbohydrates, they are broken down into glucose, which enters the bloodstream. Insulin helps glucose enter cells, where it is used for energy production or stored for later use. By facilitating the uptake of glucose, insulin helps to maintain blood sugar levels within a narrow range. Without insulin, glucose cannot efficiently enter cells, leading to high blood sugar levels (hyperglycemia). Option 3 correctly states that the main function of insulin is to control the level of sugar in the body. It is essential for individuals with diabetes, as they either do not produce enough insulin (type 1) or do not respond properly to it (type 2).