__nothing can be done to change it.Р A. begins B. having begun C. beginning D. begunР 【解析】 :本题考查的是过去分词作条件状语从句时的用法.在这儿once begun可换成once it is begun,故最佳答案是D项.Р【名题20】 (2002上海春招)Р When _______, the museum will be open to the public next year.Р A. completed B. completing C. pleted D. to pletedР 【解析】该题考查过去分词充当时间状语的用法.pleted还原成when it pleted便可知最佳答案为A.Р【名题21】 (2002合肥市高三第二次抽样考试 · 28)Р ______ who she was, she said she was Mary’s cousin.Р A. Asked B. When asked C. When asking D. AskingР 例:⑴ Once recovered, he went all out to do his work.Р ⑵ Though beaten by the opposite team, the players didn’t lose heart.Р ⑶ If carefully done, the experiment will be essful.Р 要学习掌握非谓语动词作状语,就必须牢记不定式、现在分词和过去分词的基本属性,并据此从句子的整体结构去理解句子的含义。只有这样,才能有效地排除干扰项,并作出正确选择。