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

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(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。