Question

bones work with the system to allow gross movements such as running and smiling. integumentary muscular endocrine cardiovascular

Explanation:

The muscular system contracts and relaxes to move bones. For example, when running, leg muscles (like quadriceps and hamstrings) pull on leg bones. When smiling, facial muscles (like zygomaticus major) pull on facial bones. The integumentary system (skin, hair, nails) protects the body. The endocrine system (glands like thyroid) regulates body functions via hormones. The cardiovascular system (heart, blood vessels) circulates blood. Only the muscular system directly enables gross movements by working with bones.

Answer:

muscular