prep1-3 一个百思不得其解的问题

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

选a

其他的选项错误我都明白。但是a选项 为什么less than 35 years...前面不加in呢，怎么也想不通！求nn指教！

可不可以这样理解：Their descendants, (popularly known as killer bees,) had migrated as far north as southern Texas (Less than 35 years ) after the release of African honeybees outside Sao Paulo, Brazil.

up

In my opinion:

In less than 35 years: it means that the action of migration finishes in the period of 35 years, therefore, the correct verb tense should be the past verb tense

Less than 35 years: it means that a time point (35 years after the release of ...), as the release of ... happened in the past, the correct verb tense should be the past perfect