Answer:
1. The skeleton, Muscle, and skin.
2. Why they are always together.
3. Skins give vitamin D which is essential for the formation of calcium stored in the skeleton.
4. It helps the skeleton to move. You cannot go anywhere and do anything without it.
5. Skeleton cannot move without skin and muscles because muscle makes the skeleton flexible, muscles are also necessary for movement: They're the masses of tough, elastic tissue that pull our bones when we move, while the skin provides a protective barrier against mechanical, thermal and physical injury and hazardous substances. Prevents loss of moisture. Reduces harmful effects of UV radiation and covers and protects everything inside your body. Without skin, people's muscles, bones, and organs would be hanging out all over the place.
