he had won the first prize, he felt very happy.A. KnowB. KnownC. KnowingD. Being known

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A. Know
B. Known
(答案→)C. Knowing
D. Being known
解析：考查非谓语动词。句意：知道了他已经获得了一等奖，他感到非常高兴。现在分词表示正在进行的伴随性的动作，其逻辑主语为句子主语，谓语句首可表示原因等。故选C。