Answer
c.
Work Step by Step
Option a. is incorrect. The period between noon and 6:00 P.M. saw the highest pH, which means the pond water was at its most basic level.
Option b. is incorrect. At noon, the pH was at 8, which is at a basic level and is not acidic.
Option d. is incorrect. At 6:00 P.M., the pH was at 7.5, which is at a basic level.
Option c. is correct. Between the hours of midnight and 6:00 A.M., the pH level of the pond was under 7, meaning that the water was acidic during this period of time.
