Researchers notice that animal populations in a wildlife preserve have been decreasing. Which step should the researchers perform to obtain the most valid data about the decreasing animal population?
O A. analyze data about areas of the preserve that require extensive maintenance
B. count and track the number of guests visiting the preserve on a weekly basis
C. throughout the year count and record animals throughout the preserve, as well as log animal deaths
O D. interview current and former employees about their favorite animal found in the preserve