Which of the following is true about clean energy according to Paragraphs 5 & 6?

答案：[C] Its continuous supply is becoming a reality.

解析：这是一道细节题，根据题干给出的5-6段和主题词clean energy，回到原文的第5-6段。这两段都不长，第五段But后讲到电池容量的提升a boost in the storage capacity，与clean energy并不是因果关系，与A选项不符，故排除；B选项说到广泛用在汽车制造业也不符合原文第六段第一句；D选项和原文第六段最后一句是语义相反的，故也排除；而选项C和第五段最后一句语义一致，也和全文主题一致，故为正确答案。