问题补充:
Carbon dioxide from burning fuels is the most common of the so-called greenhouse gases.
A. producing
B. having been produced
C. to be produced
D. produced
答案:
A. producing
B. having been produced
C. to be produced
(答案→)D. produced
解析:此题为非谓语动词的考查,因为carbon dioxide 与produce 之间是动宾关系,所以 用过去分词表示被动。故选D。