1. I think you should buy the blue one.
That's a good idea.

2. I don't think you should sell your car.
Thanks for the advice, but I really need the money.
 

3. Let's go bowling tonight.
Sorry, I can't. I'm meeting a friend for dinner.
 

4. Why don't we go skiing on Saturday?
Sounds like a good idea. Where do you want to go?
 

5. Why don't you come with me to China?
Thanks, but I've already been there.