In her younger years, she __________ five kilometers daily.

Explanation

The correct answer is A) walked because it correctly indicates a habitual action in the past. Options B) had walked and D) had been walking imply actions completed before another past event, which is not indicated here. Option C) has been walking is present perfect continuous, unsuitable for a past habit. Option E) was walking suggests an action in progress and is less appropriate for expressing a regular past routine.