这题用白勇的语法全解怎么解释不通啊?

SuJie0481010

Retailers reported moderate gains in their November sales, as much because of their sales of a year earlier being so bad as that shoppers were getting a head start on buying their holiday gifts.

 

1. of their sales of a year earlier being so bad as that
2. of their sales a year earlier having been as bad as because
3. of their sales a year earlier being as bad as because
4. their sales a year earlier had been so bad as because
5. their sales of a year earlier were as bad as that

  这题选D,但是 SO .....AS .....不是只能用在否定句中吗(根据白勇语法全解)

SuJie0481010

谢谢了！偶明白了！