In 2018, Orville made a taxable gift of $25,000 to his brother, Wilbur. In 2021, Orville died, and his entire estate passed to his son, Ken. Which of the following may increase as a result of Orville's 2018 gift? The total:

A)Estate tax paid by Orville's estate.

B)Gift tax paid by Ken.

C)Gift tax paid by Wilbur.

D)Income tax paid on Orville's final federal tax return.