单选题 Because cows ______ meat and milk, they are valued in many countries.

【正确答案】 C
【答案解析】product为名词，而空格处应为该句谓语动词，首先排除选项B、D。both为并列连词，并列同等成分，此处并列的应为meat和milk，谓语动词应置于并列结构之外。故应选C。