The correct answer is A. I always get good grades.
Explanation
The word "Although" is used to introduce contrasting ideas or sentences. In this context, a sentence with the opposite meaning should be added. Therefore, if the first sentence is about a negative practice such as "Although I don't study very much..", the most appropriate for the second sentence would be a sentence in which a positive practice or consequence stands out "I always get good grades." So, the correct answer is A.
