Which of the following statements is true?

the organ system is the lowest level in the hierarchy.
organ systems are less complex than the organs they are made from.
the success of a system depends on the proper function of its parts.
the muscular system does not need the skeletal system to move the body.

The success of a system mainly depends upon the effective functioning of parts in the system.

Option (c);

EXPLANATION:

The system of organs refers to the successful working of the organs, body parts and tissues together. Each of the parts mainly depends upon the other system for their effective functioning. The circulatory system which carries oxygen, blood, and nutrients to all parts of the body works in coordination with the respiratory system which exchanges carbon dioxide for oxygen with blood. Now, all the wastes of the body are eliminated with the help of digestive and urinary systems. Thus, we see that the success of the system depends on the proper function of its parts.