8. Parker is a dog whisperer who has consulted with some of the most famous Hollywood stars and their canine friends. He issued an invoice on December 1st and received a check in the mail on December 30th. Which of the following doctrines requires that he includes the income as taxable in the current year and not defer it to the following year?

A. The doctrine of constructive receipt.

B. The economic benefit doctrine.

C. The doctrine of the fruit and the tree.

D. All of the above are key tax principles underling personal income taxation.