The correct answer is option (B) It must be mitochondria.
Mitochondria are called the power houses of the cell. It is because these organelles act similar to the digestive system. They take in nutrients, break down and digest them producing energy rich substances called the adenosine triphosphate (ATP). A few cells like the muscle cells have numerous mitochondria as they need lot of energy. The number of mitochondria is based on the energy requirement of the cell. Mitochondria can grow, divide and even fuse with the other mitochondria.