Plants are more efficient at acquiring carbon than are fungi, in the form of carbon dioxide, and converting it to energy-rich sugars.

 A

Plants are more efficient at acquiring carbon than are fungi,

 B

Plants are more efficient at acquiring carbon than fungi,

 C

Plants are more efficient than fungi at acquiring carbon,

 D

Plants, more efficient than fungi at acquiring carbon,

 E

Plants acquire carbon more efficiently than fungi,

【申友解析】

正确答案：C

考点：平行。
选项分析
A. 主系表结构的比较后面的are多余；后面的in the form of carbon dioxide错误的修饰了fungi；converting应当与acquiring平行。
B. 比较对象错误同A。修饰错误同A。
C. 正确。
D. ", more efficient than fungi at acquiring carbon,"作为插入语，使得句子没有谓语东西，并且and没有平行对象。
E. 比较对象错误同A。修饰错误同A。