Answer:
It would be the first one (3, 4, 6, 7, 9)
Explanation:
The symbol ∪ of M∪N means union, and it indicates that the the new set M∪N will be comprised by the combination of the data of M and U including the intersection of both.
In the image the set M = (3, 4, 7, 9) and the set N = (4, 6, 7), the intersection is (4, 7) so the union of M∪N, will include all those values.