A zookeeper is monitoring the population of gazelles. The herd needs three times more males than females to thrive, and the zoo only has room for 12 female gazelles. Let x = the number of female gazelles and y = the number of male gazelles. Write the constraints to represent a thriving population of gazelles at the zoo.

A.x > 0 and y > 0
B.0 < x ≤ 12 and 0 < y ≤ 36
C.0 < x ≤ 12 and y > 36
D.x > 0 and y < 23