Which of the following sets represents the domain of the function shown? (5 points) {(2, 3), (4, 7), (5, 9), (11, 6)}
a
{2, 4, 5, 11}

b
{3, 7, 6, 9}

c
{(3, 2), (7, 4), (9, 5), (6, 11)}

d
{2, 3, 4, 5, 6, 7, 11}