Question

(viii) I................ walk three kilometers daily in my childhood.
(would, should, used to)​

Answer 1

I used to walk three kilometers daily in my childhood.

Answer 2

Answer:

I used to walk three km daily in my childhood.

Explanation:. Used to is the perfect option , Here, in your sentence wants to explain a habit of far past. So on that time this work happened during a time period.