A total of $$42$$ chickens and rabbits are caged together. If there are $$124$$ legs in total, how many chickens and rabbits are in the cage, respectively? 
选项为:A:$20$; $12$  B:$22$; $20$  C:$20$; $24$  D:$19$; $21$  请回答其中一个选项.