From the following options, identify which would be considered a taxable gift.

a. An author gave his right to future royalties to his daughter. b. A father established a revocable trust five years ago and last month changed the beneficiary of the trust to his daughter. c. A mother added her son as a joint owner of a brokerage account. d. A father establishes an irrevocable trust with his children as beneficiaries but has not decided which assets to place in the trust.