f(-0)=-f(0)
所以f(0)=0
f(3)=f(6)=f(0)=0
f(-2)=-f(2)=0
f(1)=f(-2+3)=f(-2)=0
f(4)=f(1)=0
f(5)=f(2)=0
所以,共有12345五个解,选A.