To determine if an employer is a monthly or semiweekly depositor for 2021, the lookback period is:

a. January 1 - December 31, 2019.
b. July 1, 2019 - June 30, 2020.
c. October 1, 2019 - September 30, 2020.
d. January 1 - December 31, 2020.