单选题 Rhetorical Device: 生态是统一的自然系统,是相互依存、紧密联系的有机链条.人的命脉在田, 田的命脉在水,水的命脉在山,山的命脉在土,土的命脉在林和草. An ecosystem is an integrated natural system of interdependent and closely-related ecological chains. The lifeline of humans rests with farmlands, that of farmlands with water, that of water with mountains, that of mountains with earth, and that of earth with forests and grasslands