Michal accidentally omitted from her 2012 tax return $ 4,000 of gross receipts she collected as the

Question:

Michal accidentally omitted from her 2012 tax return $ 4,000 of gross receipts she collected as the owner of a restaurant. Her 2012 return indicated collective gross receipts of $ 35,000. The IRS no longer can pursue Michal with the threat of collection of the related tax, interest, and penalties as of April 15, ___
a. 2014
b. 2016
c. 2019
d. 2020
e. There is no expiration date for the statute of limitations in this context.