1. I have been looking for my keys.
2. He has been crying because he didn't want to go to the dentist.
3. No, you haven't. I have been reading this since morning, so thanks for returning me to the real world. I have a lot of work to do.
4. No, you haven't. I have been waiting for you for only a few minutes.
5. I have been thinking about my friend who doesn't want to talk to me anymore.
6. Please, help me. I have been doing this homework for 2 hours!