The system works with the nervous system to protect important organs such as the brain and spinal cord.

skeletal

Explanation:

The bone system (or skeletal system) is made up of bones and skeleton, bones and cartilage. There are 206 bones and these are of different sizes and shapes.

Some may be tiny bones such as those in the ear (hammer, anvil and stirrup). The total length of the ossicles chain can measure 18 mm. There are also long bones, among them the longest in the human body is the femur that can measure up to 60 cm.

The main function of this system is to support the body, help locomotion and protect internal organs like brain and spinal cord. Bones are classified according to their shape into long, short, flat and irregular.

the answer is the last option or letter d)