Answer :
Let H represent heads and T represent tails.
Writing HH means we get two heads and HT means we get heads first, then tails second, and so on.
We have these four possible outcomes when flipping two coins
- HH
- HT
- TH
- TT
Of those four outcomes, two of them have exactly one head show up (HT and TH). The probability of getting exactly one head is 2/4 = 1/2, so this is why Jose is correct.