Concept:The heart is made of a special type of muscle tissue that is designed to contract continuously and resist fatigue throughout life.
Explanation:Cardiac muscles are found only in the wall of the heart.
These muscle fibres have their own rhythmic contraction ability, called myogenic activity.
They are supplied with abundant mitochondria, which allow sustained aerobic respiration for continuous energy production.
Unlike skeletal muscles, cardiac muscles never become tired or fatigued because of their specialised structure and blood supply.
Smooth muscles contract slowly and are not responsible for the heart's pumping action.
Therefore, the continuous beating of the heart without fatigue is due to the presence of cardiac muscles.
Answer:C. cardiac muscles