27. To maintain forests as valuable “carbon sinks,” we may need to ___

27.【答案】 [A] lower their present carbon-absorbing capacity

【解析】答案在文中第二段。文中提出针对“carbon sinks”的解决方法为reducing their capacity to sequester carbon now，与选项A一致。B选项是加快树苗的生长，根据后文可知与原文意思相反。C选项说需要在不同种类的植物之间保持平衡，但文中是It involves striking a subtle balance，混淆概念。D选项未提及。故选择A。