On Dec 12, 2020, Vancouver Photography, received $ 6,000 from a customer as an advance payment for some work to be done. The payment was credited to Service Revenue. Twenty percent of the work was performed in December 2020, with the rest to be done in January 2021, at which time the customer will be billed. The required adjusting entry at December 31, 2020 (year end) is

O a. Dr. Service Revenue $ 1,200, Cr. Unearned Revenue $ 1,200.

Ob. Dr. Service Revenue $ 4,800, Cr. Unearned Revenue $ 4,800.

Oc. Dr. Unearned Revenue $1,200, Cr. Service Revenue $ 1,200.

O d. Dr. Unearned Revenue $ 4,800, Cr. Service Revenue $ 4,800