It is said that sixty percent of all energy in the world today is being lost as wasted h

问题补充：

It is said that sixty percent of all energy in the world today is being lost as wasted heat.

A. produced

B. producing

C. to produce

D. having produced

答案：

(答案→)A. produced

B. producing

C. to produce

D. having produced

解析：A 考察非谓语动词。据说现在世界上生成的所有能源的百分之60都是以废热的形式浪费掉了，produce和句子谓语is之间满意连词，故使用非谓语形式。Produce和逻辑主语energy之间逻辑上构成被动关系。用过去分词做后置定语。故A正确。