a scientist conducts an experiment to determine how the co2  levels in ocean water affect the number of plants that can grow in the ocean. what is the dependent variable?   co2  level  number of plants  plant height  types of plants

The dependent variable is 'Number of plants' which is the correct answer.

The independent variable is CO₂ levels in ocean water, however, the growth of plants in ocean water depends on the CO₂ levels. Higher CO₂ is level is conducive to the growth of plants.

Plants use CO₂ and water in photosynthesis to prepare food in the presence of light.

6CO₂ + 6H₂O + light energy = C₆H1₁₂O₆ + 6O₂.