Which of the following is an example of an executive order?

Which of the following is an example of an executive order?
 
  a. President Obama's order raising the minimum wage of federal contractors
  b. President Obama's proposal to reform health care policy
  c. President Bush's order to send troops to Afghanistan
  d. President Nixon's order to hold back funding for the Clean Water Act

Question -2-

Which of the following philosophers greatly influenced James Madison's beliefs regarding the nature of liberty?
 
  a. John Dewey
  b. John Locke
  c. Martin Heidegger
  d. Michel Foucault

Question -3-

Which constitutional amendment allowed voting by all qualified citizens aged 18 or older?
 
  a. Twenty-Sixth
  b. Fifteenth
  c. Twentieth
  d. Nineteenth