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.