Answer: The correct answer is C. 300.
Step-by-step explanation: To find out how many students in the class had a C average, we first need to determine the number of students who graduated with an A average and the number of students who got a B average.
Given that one-eighth of the class graduated with an A average, we can calculate the number of students who got an A average as follows:
Number of students with an A average = (1/8) * Total number of students
Number of students with an A average = (1/8) * 800
Number of students with an A average = 100
Next, we know that half of the class got a B average. We can calculate the number of students who got a B average as follows:
Number of students with a B average = (1/2) * Total number of students
Number of students with a B average = (1/2) * 800
Number of students with a B average = 400
Now, we can find the number of students who had a C average by subtracting the number of students with an A average and the number of students with a B average from the total number of students:
Number of students with a C average = Total number of students - Number of students with an A average - Number of students with a B average
Number of students with a C average = 800 - 100 - 400
Number of students with a C average = 300
Therefore, 300 students in the class had a C average.
The correct answer is C. 300.