Phytoplankton form the base of food webs, but are only present in the upper few hundred meters of the ocean. a number of factors here can limit their growth and hence limit the amount of biomass in higher trophic levels.

which of the items below is not one of these limiting factors to phytoplankton?

a. nitrogen

b. light

c. phosphate

d. oxygen

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.

your best option is 5,000 kg