Out of the given options, the correct answer is option 4: Glucose.

1) Urea is a waste product formed in the liver as a result of protein metabolism and is not a carbohydrate.

2) Insulin is a hormone produced in the pancreas and is not a carbohydrate.

3) Glycine is an amino acid, which is a building block of proteins and not a carbohydrate.

4) Glucose is a simple sugar and is a type of carbohydrate. It is the primary source of energy for cells and is commonly found in foods such as fruits, honey, and carbohydrates like rice and bread.

In summary, glucose is the correct answer as it is a common carbohydrate, while the other options are not.