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
OA: A
Please explain tense structure in A? The past perfect is used to indicate that an action in the past occured before another action in the past. So why is the past perfect used here? ALso what is the best approach to eliminate all wrong answers and arrive at the right one?