A penny is tossed. We observe whether it lands heads up or tails up. Suppose the penny is a fair coin; that is, the probability of heads is one-half and the probability of tails is one-half. What does this mean? a. Every occurrence of a head must be balanced by a tail in one of the next two or three tosses. b. If the coin is tossed many, many times, the proportion of tosses that land heads will be approximately one-half, and this proportion will tend to get closer and closer to one-half as the number of tosses increases. c. Regardless of the number of flips, one-half will be heads and one-half tails. d. All of these answers are correct.