Answer:
skeletal system and the muscular system,
Muscles are attached to the skeleton and work assuming that the skeleton is there - for example there is no muscle that makes sure you don't bend the middle of your arm, as it's stable because there is a bone in it. Basically, the skeleton is a scaffolding for the muscles
the skeletal system and the nervous system,
Many nerves run along the skeleton, or even inside the bones and the bones protect the nerves - for example in the spinal cord
the muscular system and the nervous system.
Nervous system controls the muscles! it sends them messages such as "move the muscle now" - and in fact the muscles are directly connected to the skeletonExplanation:
