Some people argue using nature to meet our own needs may spell disaster, unless we start

Some people argue using nature to meet our own needs may spell disaster, unless we start to look around and understand how clean environment benefits us all.
A. /; a
B. the; the
C. the; a
D. a; a

(答案→)A. /; aB. the; theC. the; a D. a; a解析：考查冠词;第一空不填，nature是抽象名词，第二空填a，指一个清洁的环境，句意是：有些人认为利用自然来满足我们的需求可能会带来灾难，除非我们开始环顾四周，理解一个清洁的环境怎么使我们所有人的受益。

回答的不错