On March 15, 2015, a corporation filed its 2014 calendar year tax return showing $120,000 gross income. The return was prepared by a CPA who mistakenly omitted $45,000 of income, which the CPA considered in good faith to be nontaxable. No information with regard to this omitted income was disclosed on the return or attached statements. By what date must IRS assert a notice of deficiency before the statute of limitations expires?
A)April 15, 2018
B) December 31, 2017
C) March 15, 2021
D) March 15, 2020