Complete these sentences with say/says or tell/tells 3. Parents often ... their children bedtime stories.

Parents often tell their children bedtime stories. - Родители часто рассказывают своим детям сказки на ночь.

We can't use say / says in this sentence ae say is translated - сказать.

We can't use tells because - s is the suffix of Present Indefinite which we use in the third person singular. Parents - is in the third person but not singular. Parents is in plural. (parent + s). That's why we use tell. Often is one of the keywords of Present Indefinite.

If we have Parent instead of Parents we use tells.

Parent often tells their children bedtime stories.