请教各位版主和高人, gwd 26-20

20. GWD26-Q20

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.

A.    chores; by 1997 they had spent nearly six hours
  a week

B.    chores; by 1997 that figure had grown to nearly
  six hours a week

C.    chores, whereas nearly six hours a week were
  spent in 1997

D.    chores, compared with a figure of nearly six hours a week in 1997

E.     chores, that figure growing to nearly six hours a week in 1997

gwd大全答案说b, 个人不太认同. 看了过去的讨论帖也没有一个比较有说服力的解释.

固然, by+年份理应用完成时, 但这里用完成时就使得grown这个动作发生在1981之前了.

我觉得E, 同位语结构用于该句子比较合理; 否则就C, 语法上没有太多错误.

不知道各位高人是如何认为的?

B应该是正确的吧

首先从句子两部分的关系来看就应该用 ；

A和B里就肯定是B了

E的时态是有问题的 growing 是来干嘛的呢 

had done 发生在过去的过去, 一个by 1997的数据发生在 1981之前就不合逻辑了.

growing这里是独立主格的一部分.

ding