9. Which of the following relations are functions? Choose all that apply. Assume that each different variable
has a different value.
{(a,b),(0,0),(c.c),(e,d)}
{(c,e),(c,d),(0,b)}
{(6,5),(c,d),(d.c),(0,0)}
{(a,b),(b,c),(c,d),(d,e)}