Answer:
The probability of an eighth grader winning is 1/3
Step-by-step explanation:
Total no. of students = 42
Number of students in 7th grade = 21
Number of students in 8th grade = 14
Number of students in 9th grade = 7
Probability of event = 
So,the probability of an eighth grader winning= 
Hence The probability of an eighth grader winning is 1/3
I believe the answer is A
B I hope it helps for you