关于had……GWD一个题求助

sjray637

In 1981 children in the United States spent an average of slightly less than two and a half hours a week doing household chores; by 1997 they had spent nearly six hours a week.

• Achores; by 1997 they had spent nearly six hours a week  分析A选项
• Bchores; by 1997 that figure had grown to nearly six hours a week  分析B选项
• Cchores, whereas nearly six hours a week were spent in 1997  分析C选项
• Dchores, compared with a figure of nearly six hours a week in 1997  分析D选项
• Echores, that figure growing to nearly six hours a week in 1997  分析E选项
  

这个题楼主选了C……然而，答案是楼主秒杀的一个选项，为啥81年用spent，97年都能用had grown了？！！
这是几个意思啊……

yxlrei

1981指代的事件是1981年发生的(in 1981)，是一个精确的过去。
1997指代的事件是1997年之前就已经开始发生的(by 1997)，是一个过去的过去。

sjray637

yxlrei 发表于 2015-8-29 21:34
1981指代的事件是1981年发生的(in 1981)，是一个精确的过去。
1997指代的事件是1997年之前就已经开始发生的 ...

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