Cynthia's 2018 income tax return was due on April 15, 2019. She did not obtain an extension to file until October 15, 2019. She mailed her return on August 10, 2019, and it was received by the IRS on August 15, 2019. Assuming there is no reason why the standard statute of limitations would not apply, when does the statute of limitations on assessment expire for Cynthia's 2018 income tax year? Select one: a. December 31, 2021 b. April 15, 2022 c. August 10, 2022 d. August 15, 2022 e. October 15, 2022