Which of the following statements is a necessary truth? If unicorns exist, then I will be happy. If unicorns exist, then I'll throw a party on Saturday. If unicorns exist, they have a horn on their forehead.
a) If unicorns exist, I will be happy.
b) If unicorns exist, I'll throw a party on Saturday.
c) If unicorns exist, they have a horn on their forehead.
d) None of the above.