Answer:C The students who failed the exam also had poor attendance.
Explanation:If the students did not attend the class it means they did not get most out of the lecture and they probably missed out on most lessons hence that can also be used to explain the failing rate.
When that can be true then the blame can not be 100% on the professor's ability to teach because if he is teaching and they are not present it can be expected that they will not do well on the subject whether he is good or not .