He didn't know about that thing.

In ancient times, ministers had to stand before the emperor to report important matters.

The emperor stands at the highest position in the country.

Once upon a time, there was a big castle in this place.

Health is very important.

His opinion is very important.

Your cooperation is needed for this project.

I need you.

Once, we used to play in the park every day.

In the past, we used to play in the park every day.