d = {x|x is a whole number} e = {x|x is a perfect square between 1 and 9} f = {x|x is an even number greater than or equal to 2 and less than 9} which of the following is d ∩ f? a. {4, 6} b. {2, 4, 6} c. {2, 4, 6, 8} d. {2}