prep1-163 关于过去进行时的一点困惑

The British sociologist and activist Barbara Wootton once noted as a humorous example of income maldistribution that the elephant that gave rides to children at the Whipsnade Zoo was earning annually exactly what she then earned as director of adult education for London.

(A) that the elephant that gave rides to children at the Whipsnade Zoo was earning

(B) that the elephant, giving rides to children at the Whipsnade Zoo, had been earning

(C) that there was an elephant giving rides to children at the Whipsnade Zoo, and it earned

(D) the elephant that gave rides to children at the Whipsnade Zoo and was earning

(E) the elephant giving rides to children at the Whipsnade Zoo and that it earned

对于答案A没有争议，但是关于A中的that从句里使用的过去进行时was earing实在是费解。

还原that从句，省略掉修饰成分的化，就是the elephant was earing annually exactly what she earned ……

为什么用过去进行时呢？用过去时不是更平行吗？

请指教！

我想用进行时更能体现对比：Barbara earned的同时the elephant was earning；如果都用过去时，形式上对称，逻辑上不能体现两动作发生在时间上的可比性。

虽然我简单的理解了一下ls的说法，但是可否说的再清楚一点啊？

我比较笨……

我想这个题之所以用was earning是和前面的语言环境有关系的，前面说Barbara Wootton once noted，BW曾经注意到一件XX样的事情，为了表明就在BW注意的那一时候，大象正在earn，所以用过去进行时更好些。就像我们可以说“我昨天看见他正偷东西”一样。  因此我认为并不是和后面的she then earned对照时间发生的前后的。

还有就是我觉得GMAT中，时态是最难用来判断正误的，所以除了是一些很明显的时态错误，尽量不要一上来就用时态排除选项

哦对了，grape吼吼，熟人啊~~你好

The British sociologist and activist Barbara Wootton once noted as a humorous example···

请达人帮忙分析一下这个句子的结构 sb once noted as sth ？ 感觉 as 有点多余啊~~