To say that a coin is "fair" means that when it is tossed, each of the outcomes (heads or tails) has a 50% probability of occurring. This means:

a. in the next six flips of the coin, at least three of the outcomes will be heads.
b. in the next six flips of the coin, exactly three of the outcomes will be heads.
c. in the next 6000 flips of the coin, approximately 3000 of the outcomes will be heads.
d. in the next 6000 flips of the coin, exactly 3000 of the outcomes will be heads.