2. Have you ever lost your key?

Actually, I've never lost my keys because I don't carry a case with me.

Yes, I have lost my keys a few times. Once, I was rushing to school and I lost them. Another time, I lost them on the street. I had to retrace my steps to find them.

Certainly. It's a past event. I lost my key at someone's house. I had to arrange for a locksmith to open the door. It was a terrible experience. It taught me to be more careful in some situations.