Explanation:

- Option 1: Nucleus

- The nucleus is the control center of a cell. It contains genetic material (DNA). It is not a pore on leaves.

- Option 2: Stomata

- Stomata are tiny pores on the leaf surface.

- They help in gas exchange (carbon dioxide in, oxygen and water vapor out).

- Vital for photosynthesis and transpiration.

- Option 3: Mitochondria

- Mitochondria are powerhouses of the cell.

- They produce energy (ATP) through respiration and are found in cells, not on leaf surfaces.

- Option 4: Cytoplasm

- Cytoplasm is the jelly-like substance inside the cell.

- It surrounds cell organelles, and is not a pore.