Answer:
C. If you flip a coin, it will come up either heads or tails.
Explanation:
A. My guess is it doesn't rain much in Phoenix in July. A probability of 1 means it will happen for sure, so this is not it.
B. A die has 3 even numbers and 3 odd numbers. The probability of rolling an even number is 3/6 = 0.5. This is not it.
C. If you flip a coin, you either get heads or tails. The probability of heads or tails is 1 since one of the two outcomes will always happen. This is the answer.
D. The probability of the birth of a girl is 1 out of 2, so it is 0.5. This is not it.