In 2004, tests were performed on the San Carlos Reservoir in Arizona to determine levels and distributions of some toxic metals. Cores of sediment were sampled and tested, and the scientists found that there were two time periods represented in the sediment by larger levels of copper than is recommended in sediment quality guidelines. What scientific investigation might these results lead the scientists to next?A. a study of the rate of evaporation of the water in the reservoirB. a study of companies that might dump toxic metals into the oceanC. a study of what plant species are native to various regions of ArizonaD. a study on how copper affects aquatic life in the reservoir