Concept:Mitochondria are called the powerhouse of the cell because they produce most of the cell's energy in the form of ATP through cellular respiration.
Explanation:Mitochondria have a double membrane and generate adenosine triphosphate (ATP), which is used as the main energy source for all cell activities.
The number of mitochondria in a cell depends on its energy needs. For example, muscle cells have many mitochondria.
Other options do not produce energy:
The cell wall only gives structural support in plants and fungi.
Ribosomes are involved in protein synthesis, not energy production.
The nucleus controls cell activities and stores DNA, but it does not generate energy.
Hence, only mitochondria are correctly known as the powerhouse of the cell.
Answer:B. Mitochondria