Which of the following body systems pertains to the intestines and related organs?

The gastrointestinal system is the correct choice because it encompasses the organs involved in the digestion and absorption of food, as well as the elimination of waste. This system includes the intestines, stomach, liver, pancreas, and other related organs that facilitate these processes. It plays a crucial role in breaking down food into nutrients, which are then absorbed into the bloodstream, while also managing the removal of undigested materials.

The other body systems listed are distinct in their functions: the endocrine system is involved in hormone production and regulation, influencing various bodily functions; the musculoskeletal system includes bones, muscles, and connective tissues that provide structure and movement; and the genitourinary system is responsible for the production and excretion of urine as well as reproductive functions. Each of these systems is vital, but only the gastrointestinal system directly pertains to the intestines and their associated structures.