Carl purposely omitted from his 2014 tax return $ 40,000 of the gross receipts that he collected as the owner of a restaurant. His 2014 return indicated collective gross receipts of $ 25,000. The IRS no longer can pursue Carl with the threat of collection of the related tax, interest, and penalties, as of April 15, ___
a. 2016
b. 2019
c. 2021
d. 2022
e. There is no expiration date for the statute of limitations in this context.