Answer:
Option: C is correct.
( C.] He should have represented the number of students on the vertical axis to show its variation over time ).
Explanation:
Pedro was incorrect with his graph.
As the frequency or the amount of any quantity is always represented by the vertical axis.
and as we are seeing the data of every month so every month should be treated as input and should be kept on the horizontal axis and the resulting value i.e. the number of students going to his school on that month is the output and it should be represented on the vertical axis.
Hence, option C is correct.
C.] He should have represented the number of students on the vertical axis to show its variation over time.