Weshouldkeepb___betweenbodyandmindAabalanceBbalanceCbalanceDabalaced可是答案选C为什么这儿用名词不形容词KEEP不是+形容词吗?

　　Weshouldkeepb___betweenbodyandmind

　　AabalanceBbalanceCbalanceDabalaced

　　可是答案选C为什么这儿用名词不形容词KEEP不是+形容词吗?