第1个回答 2013-08-21
这是个以only开头的句子，所以后面的主要谓语动词realize要倒装，从而导致在realize前面he的前面多了did.
整句结构:
Only when … the police:整句的时间状语(从句);
(did) he :主语;
realize:主要谓语动词
that they … hoax:宾语。
第2个回答 2013-08-21
Only （副词，状语）when he saw that the man was actually telephoning the police（时间状语从句） did he（主语） realize（谓语） that they had all been the victims of a hoax（宾语从句）.
时间状语从句中：
he （主语）saw（谓语） that the man was actually telephoning the police（宾语从句）.
这是个倒装句，正序为
He(主语) realized（谓语） that they had all been the victims of a hoax（宾语从句）only when he saw that the man was actually telephoning the police（时间状语从句）.本回答被提问者采纳
第3个回答 2013-08-21
这是一个含有时间状语从句的主从复合句。主句是did he realize that they had all been the victims of a hoax.
在英语中，如果由only以及和它所修饰的状语位于句首时，主句要用倒装语序。
这个句子的正常语序是：
He realized that they had all been the viticms of a hoax only when he saw that ...
第4个回答 2013-08-21
Only【 when he saw （that the man was actually telephoning the police 宾语从句）时间状语从句】 【did谓语动词的一部分】 【he 主语】【 realize谓语动词的一部分】【 that they had all been the victims of a hoax宾语从句】.
整体句子结构：
Only+时间状语从句+did sb do sth 倒装句
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