Correct option is C
To calculate the average pH of the lake water over the six days, we take the sum of all pH values and divide it by the number of days.
Given pH values over six days:
10.5, 10.3, 10.1, 10.4, 10.7, and 10.4
Step 1: Sum of all values:
10.5 + 10.3 + 10.1 + 10.4 + 10.7 + 10.4 = 62.4
Step 2: Divide the sum by the number of observations (6):
62.4 ÷ 6 = 10.4
10.4 is close to 10.36 so option C is correct answer.