Which experiment describes a binomial experiment?

a) draw 4 cards from a deck of cards, without replacement, and record each time the card is an ace.
b) roll 2 number cubes until rolling a sum of 8 and record how many trials you made.
c) ask 9 people the same question and record each time they answered yes, no, maybe.
d) spin a spinner with sections labeled a through f 6 times and record each time you get a vowel.