The table Arc(x,y) currently has the following tuples (note that there are duplicates): (1,2), (1,2), (2,3), (3,4), (3,4), (4,1), (4,1), (4,1), (4,2). Compute the result of the query:
SELECT a1.x, a2.y, COUNT(*)
FROM Arc a1, Arc a2
WHERE a1.y = a2.x
GROUP BY a1.x, a2.y;
Which of the following tuples is in the result?
a. (3,1,2)
b. (1,3,4)
c. (2,4,6)
d. (3,2,6)
Answer: A