What is the most likely explanation for the smaller size of the hypoxic zone in the year 2000? select one: a. an increase in fertilizer dumping in rivers b. decrease in the amount of sediments carried into the gulf c. decreased amounts of phosphorus and nitrogen in the gulf d. increased growth of phytoplankton

The correction option is A.
Hypoxic zone refers to low oxygen areas in the oceans and large lakes. Hypoxic zone is always caused by large amount of excessive nutrients pollution that arise from human activities such as dumping of factory wastes and fertilizers in water bodies. These excessive nutrients usually reduce the concentration of oxygen in these water bodies.