In which, if any, of the following independent situations does the Federal gift tax apply?

a. Trent established a revocable trust, income payable to himself for life and, upon his death, remainder to his children

b. Trent pays $5,000 tuition to a local university for his grandsons benefit

c. Trent sends $25,000 to Alices oral surgeon in payment of her dental implants. Alice is Trents sister and does not qualify as his dependent

d. Trent pays his fathers rent for the month. His father is not his dependent