1. What must people do because of scarcity?
   
   
2. When do economic interactions between people occur?
   
   
3. Where do economic interactions occur?
   
   
4. What are opportunity costs?
   
   
5. What is comparative advantage?
   
   
6. Why are there gains from international trade?
   
   
7. Why are there increasing opportunity costs?
   
   
8. Why is the production possibilities curve bowed out?
   
   
9. What are the three situations defined by the production possibilities curve?
   
   
10. Why are points outside the production possibilities curve characterized as impossible?
    
    
11. How does economic growth affect the production possibilities curve?
    
    
12. What are the three essential questions faced by every economy?
    
    
13. Name four characteristics of market, but not command, economies.
    
    
14. What is the difference between market failure and government failure?
    
    
15. What are the three roles of prices in a market economy?