Instructions: Given a passage with a question and an answer to that question, classify if the answer actually answers the question into 'yes' or 'no'. Output 'yes' if the answer answers the question and output 'no' if the answer does not answer the question.
Input: Question: Is mitochondrial DNA copy number associated with diagnosis and prognosis of head and neck cancer?
Answer: mtDNA copy number appears to be associated with HNC stage and survival, but confirmation requires similar studies in larger cohorts.
Output:
yes