- A1/2
- B35/128
- C99/128
- D1/128
Step-by-Step Solution
Seven is odd, so a tie is impossible and every outcome is a win either for heads or for tails. Turning every head into a tail and every tail into a head pairs the outcomes off exactly, matching each 'more heads' outcome with a 'more tails' one, so the two events must be equally likely and the answer is 1/2 without any counting. Counting confirms it: at least 4 heads happens in of the outcomes, and 64/128 = 1/2. The option 35/128 counts exactly four heads, 99/128 answers 'at least three heads', and 1/128 is all seven heads.
Answer: A) 1/2