Answer:
a.
Step-by-step explanation:
Based solely on the snippet of code provided on the question the main reason why the code won't compile (from the options provided) is that the setAverage() method can’t access the average instance variable. Since the average variable is an instance variable it means that it only exists inside the one of the functions and not to the entire class. Meaning that in this scenario it can only be accessed by the Student function and once that function finishes it no longer exists. Also, it is not one of the options but if these variables are instance variables as mentioned their type needs to be defined inside the function.