Nutrient pollution about Marine animals???

A) How can an increase in algal population size kill fish?

1) Algae clogs the gills of the fish, preventing them from breathing.
2) Algae clogs the mouths of the fish, preventing them from eating.
3) The algae use up the oxygen in the water as they photosynthesize.
4) When the algae die, their decomposers use up the oxygen in the water.

B) When phosphorus input was increased to 3X normal in a lake without any animals, on average how much dissolved oxygen remained in the water?

____________ mg/L

C) Which species in the lake community often experience limitation by phosphorus?

Bosmina
Green algae
Cyanobacteria
Bosmina and Green algae
Green algae and cyanobacteria

can someone help me with this 3 question please