D is the answer for 36.
31. sentence 3 best supports the main idea with a tragic example.
32. Price ceiling, controls the maximum prices that can be charged by suppliers for the commodity.
33. I think this one's marginal cost because it might take a lower the price for a little while but then permanently take a sharp turn in price making it higher.
34. I think it's voluntary exchange since the transaction for the service is free trade.
35. Increase sale bonds, the Feds wanted discounts to attract new buyers.
37. A force that causes self-interest to promote the interest of society
38. I think its rational self-interest because he's thinking of himself and his own security.
Sorry I'm late :)
Oh and tell me if I'm wrong on anything.
