The correct answer is: D. Mitochondria
Mitochondria are organelles found in most eukaryotic cells. They are responsible for producing energy for the cell through a process called cellular respiration. Cellular respiration is a complex process that involves the breakdown of glucose into carbon dioxide and water. This process releases energy, which is used by the cell to power its activities.
Chloroplasts are organelles found in plant cells. They are responsible for photosynthesis, the process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen.
The nucleus is a large organelle found in most eukaryotic cells. It contains the cell’s DNA, which is the genetic material that controls the cell’s activities.
The endoplasmic reticulum is a network of tubules and sacs found in the cytoplasm of eukaryotic cells. It is involved in the synthesis and transport of proteins.
In conclusion, mitochondria are the powerhouse of the cell because they are responsible for producing energy for the cell.