Which of the following statements is correct? 
选项为:A:$$4$$ is a factor of $$38$$.  B:$$6$$ is a factor of $$72$$.  C:$$8$$ is a common factor of $$72$$ and $$84$$.  D:$$9$$ is a common factor of $$38$$ and $$72$$.  请回答其中一个选项.