Decedent, who died in the current year, owned a farm with a fair market value of $5 million. The fann was the only real property in the estate, and it constituted the major portion of the estate. Assume that the farm qualifies for valuation under section 2032A and, under the formula fann valuation method, its value is $3 million. The farm is devised to Son, who agrees to a section 2032A election. Five years after Decedent's death, Son sells the farm to an unrelated third person for $6 million. Which of the following is correct?

A. Son must pay the federal estate tax savings resulting from the use of section 2032A.

B Son must increase his income tax basis in the farm by the amount of the increase in value on which he must pay the recaptured estate tax.

C. Son must pay interest on the additional estate tax from the time the estate tax return was required to be filed until the date the additional tax is paid.

D. All of the above.