Subject: mathqa
Question: there are 24 students in a seventh grade class . they decided to plant birches and roses at the school ' s backyard . while each girl planted 3 roses , every three boys planted 1 birch . by the end of the day they planted 2424 plants . how many birches were planted ?
Option: 
A: 6
B: 5
C: 8
D: 2
Answer: A