[問題]GWD 26-20

[hilary]

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

想請問為什麼(C)不對？
雖然(B)的by+時點確實要用過去完成式，但用(C)的話，除了主動改為被動之較不好外，語句不是較簡單嗎？

謝謝大家

[dibert8]

in 1997 放句尾造成修飾歧異
這裡也有討論: http://www.formosamba.com/phpBB3/viewtopic.php?t=19985