Which sentences correctly use the words “hard” or “hardly”? I. I am exhau...

Which sentences correctly use the words “hard” or “hardly”?

I. I am exhausted because I’ve been working hard.
II. She tried hard to remember my name but she couldn’t.
III. Roger Federer is a great tennis player. He hits the ball hardly.
IV. This shirt is practically new. I’ve hardly worn it.