Which of the following is a function of the digestive system?

The digestive system has several vital functions, and one of the primary roles is breaking down food into nutrients. This process begins in the mouth with mechanical and chemical digestion and continues in the stomach and intestines, where food is further digested and absorbed. The end goal of this process is to convert the food we eat into essential nutrients, such as carbohydrates, proteins, and fats, that the body needs to function properly. These nutrients are then absorbed into the bloodstream and delivered to cells throughout the body for energy, growth, and repair.

Other options relate to different systems or functions within the body. For instance, protection against pathogens is primarily the role of the immune system rather than the digestive system. The transportation of oxygen is the function of the respiratory and circulatory systems, allowing oxygen to be delivered to tissues and organs. The production of body heat, particularly through metabolic processes, is linked to muscular and metabolic functions rather than being a direct role of the digestive system.