求助一道高中英语倒装句的题目 o(∩_∩)o

Question

Only when the whole city was covered in the thick fog _______ the importance of environmental protection.
A. people realized
B. people had realized
C. did people realize
D. had people realized
请问一下为什么这题应该选择C而不是D呢？

Answer 1

你好，同学，很高兴回答你的问题

正确答案确实选C

即： Only when the whole city was covered in the thick fog did people realize the importance of environmental protection.

翻译：只有当整个城市笼罩在浓雾之下，人们才会意识到环保的重要性。

解析：only 在句首时句子要倒装，句子为主从复合句，则主句倒装，从句不倒装。本句中从句的时态是一般过去时，那么主句的时态也要用一般过去时，不能用过去完成时，因为when 的意思是当...时，一般前后的时态应该是一致的，如果主句的动作发生在从句的动作之前，则主句用过去完成时，即“过去的过去”。而本句主句的动作应该是发生在从句的动作之后的，即先浓雾笼罩城市，后来人们才意思到，显然不能用过去完成时，所以D是错误的。

再给你看一道类似的例题，

Only when _____ home_____ that he had left his bag in the taxi he had taken.[ ]
A. he returned; did he realize
B. did he return; did he realize
C. he returned; he realized
D. did he return; he realized
Only when _____ home_____ that he had left his bag in the taxi he had taken.

A. he returned; did he realize
B. did he return; did he realize
C. he returned; he realized
D. did he return; he realized

答案：A

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Answer 2

C.only 开头部分倒装，即用助动词/情态动词放于句首
前面是过去时所以用did 倒装
D选项是过去完成时强调动作发生在whole city was covered 前与题意不符排除

Answer 3

此为Only的倒装句 the whole city was covered in the thick fog被提前，而前句有was，如果为正常语序应为people did realize，但因倒装，故选C

Answer 4

C 1）语序问题：only +状语（可能是副词、介词词组或是状语从句） 放在句首，句子需要用部分倒装（若有从句的话，注意是主句倒装）； 2）时态问题：“只有当整个城市被笼罩在浓雾之下的时候，人们才意识到环保的重要性”was covered 与realiezed 都应用过去式。

Answer 5

题中有was，说明是过去时，而realize并非发生在cover之前，故用一般过去式，选C

Answer 6

因为出现了only在句首，所以要倒装
然后从句中是was，一般过去时，主句用had 的话是发生在过去的过去，也就是was covered 之前，与句意不符。