On June 1, 2019, Emma Schulze Corporation Received $3,600 as Advance

On June 1, 2019, Emma Schulze Corporation received $3,600 as advance payment for 12 months' advertising. The receipt was recorded as a credit to Unearned Fees.
What adjusting entry is required on December 31, 2019?

A) Unearned Fees 1,800
$\quad$ $\quad$ $\quad$ Advertising Revenue 1,800
B) Unearned Fees 1,500
$\quad$ $\quad$ $\quad$ Advertising Revenue 1,500
C) Unearned Fees 2,100
$\quad$ $\quad$ $\quad$ Advertising Revenue 2,100
D) Advertising Revenue 2,100
$\quad$ $\quad$ $\quad$ Unearned Fees 2,100