Which of the Following Statements Is True

Which of the following statements is true?

A) When the forces of supply and demand determine for whom goods are produced in a society,an equitable distribution of income will naturally result.
B) An external cost will occur when some of the benefits derived from production of some good or service are enjoyed by a third party.
C) One of the roles of our government is to transfer some income from the rich and the middle class to the poor.
D) According to most economists' definition of competition,the American economy is very competitive.