是语法指代的问题.不能出现歧义.分号前后都是一个独立的句子.当然句子之间也是有一定的联系的
B.x09前面有且仅有一个figure,且明确定义了,所以用"that figure"意思就是如前所述定义的figure.
A,by 1997 they had spent nearly six hours a week （on what?究竟做什么了?没人知道）
C nearly six hours a week were spent in 1997 谁在花费时间做做什么?没人知道的啦.也是不清楚
D compared with a figure of （what figure?a是泛指,世界上任何一个figure的可以吗?）nearly six hours a week in 1997
希望帮到你哈···
这个逻辑性有点强·