18) A rational decision maker __________. A. ignores the likely effects of government policies when.

18) A rational decision maker __________. 
A. ignores the likely effects of government policies when he or she makes choices 
B. ignores marginal changes and focuses instead on “the big picture” 
C. takes an action only if the marginal benefit of that action exceeds the marginal cost of that action 
D. takes an action only if the combined benefits of that action and previous actions exceed the combined costs of that action and previous actions 

19) Lucy starts her own psychiatric practice, but her expenditures to open the practice exceed her income. Lucy is a __________. 
A. saver who supplies money to the financial system 
B. saver who demands money from the financial system 
C. borrower who demands money from the financial system 
D. borrower who supplies money to the financial system 

20) Resources are __________. 
A. plentiful for households but scarce for economies 
B. scarce for households but plentiful for economies 
C. scarce for households and scarce for economies 
D. plentiful for households and plentiful for economies 

21) What you give up to obtain an item is called your __________. 
A. explicit cost 
B. opportunity cost 
C. true cost 
D. direct cost