Prep语法2 求NN解答

egretlee

划线部分是前半句"Less than..., Brazil,"
正确答案是A. 我想问, 非划线部分，为什么用过去完成时?? 没有任何表示发生在过去的过去啊, 如果用have migrated对吗?

Less than 35 years after the release of African honeybees outside Sao Paulo, Brazil, their descendants, popularly known as killer bees, had migrated as far north as southern Texas.

A) Less than 35 years after the release of African honeybees outside Sao Paulo, Brazil,
B) In less than 35 years since releasing African honeybees outside Sao Paulo, Brazil,
C) In less than the 35 years since African honeybees had been released outside Sao Paulo, Brazil,
D) It took less than 35 years from the release of African honeybees outside Sao Paulo, Brazil, when
E) It took less than the 35 years after the time that African honeybees were released outside Sao Paulo, Brazil, and then

很困惑……会的帮忙看看吧，非常感谢！

bitieming

蜜蜂在release事件之后的35年之内就完成了从圣保罗到南德克萨斯的迁徙，迁徙是一个持续的过程，而持续时间是从35年前，到less than 35年后的一个时间点，该时间点肯定是发生在过去的~因为显然说话人在说此话时，密封已经完成了迁徙。