something hard can be used for protection & bone is hard ->  bone can be used for protection  bone can be used for protection & skeletal system is made of bones ->  the skeletal system is used to provide protection for animals  the skeletal system is used to provide protection for animals & protecting part of something helps to protect that something ->  the skeletal system protects parts of an animal in order to protect that animal  the body is a part of an animal & internal organs are a part of the body ->  internal organs are a part of an animal  the skeletal system protects parts of an animal in order to protect that animal & internal organs are a part of an animal ->  the skeletal system protects internal organs  the skeletal system protects internal organs & most major organs are internal organs -> the skeletal system protects most major organs