In order to determine the best description, first count the number of times for heads h and tails t.
Based on the given information, the number of heads was h = 6 and the number of tails was t = 18.
The theoretical probability in this case results in a 50% of probability for both events, that is, for 24 times at which the coin was flipped, 12 would be tail and 12 would be head.
Then, based on the previous explanation, you can conclude that:
C. According to theoretical probability, Avery would have expected to land on heads twite as many times as she did experimentally.