in an estuary in an open ocean at an intertidal zone at a hydrothermal vent
I gave my students this multiple choice question: Where is the biological magnification of pollutants most likely to be the greatest?

Only one answer is correct among these 4 choices:
- in an estuary
- in an open ocean
- at an intertidal zone
- at a hydrothermal vent

Could you tell me which one is correct?

in an estuary