Answer:
The correct answer is d. Oxygen
Explanation:
Phytoplanktons are responsible for the fixation of approximately half of the global carbon therefore seawater has high CO2 concentration which is required by phytoplanktons to make their food.
They are the primary producers of oceans and they are responsible to support the food chain of oceans. Factors that can limit their growth are mainly sunlight and nutrients like phosphorus, nitrogen, etc.
As phytoplanktons are photosynthetic they release oxygen itself as a byproduct therefore oxygen is not a limiting factor to phytoplanktons. So the right answer is d.
Amoebas are single-celled organisms, which means that they are composed of just one cell. Each amoeba is a cell capable of performing all living functions by itself. They can reproduce asexually. They are protozoans with no fixed shape. Most have no hard parts and look like blobs of jelly.
