Which of the following causes eutrophication
Possibly disruption in nitrogen cycle (A) is the correct answer here.
,Nitrogen, along with phosphorus is one of the crucial biogens, which concetration rise in water leads to primary producers dominating the water ecosystem, which is also known as eutophication.
,How the cycle can be disrupted by human activity? Well, pretty simple.
Use too much of nitrogen fertilizers on soil with poor retention capacity.