老PREP 3关于时态

柠檬麦胖兜

3.(24557-!-item-!-188;#058&001027)

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


原文中为什么用had migrated 过去完成时？？？？求解答！！！！！！！！