The Balance in the Office Supplies Account Had a Debit

The balance in the Office Supplies account had a debit balance on January 1, 2019, that equalled the $240 of supplies on hand. During the year, the company purchased $4,200 of supplies that were debited to the Office Supplies Expense account. The proprietor estimates that the cost of supplies remaining on hand on December 31 is $960. What is the required adjusting journal entry on December 31?

A) $$\begin{array} { | c | c | } \hline \text { Dr. Office Supplies Expense } & 3,480 \\\hline \text { Cr. Office Supplies } & 3,480 \\\hline\end{array}$$
B) $$\begin{array} { | c | c | } \hline \text { Dr. Office Supplies Expense } & 960 \\\hline \text { Cr. Office Supplies } & 960 \\\hline\end{array}$$
C) $$\begin{array} { | c | c | } \hline \text { Dr. Office Supplies } & 3,480 \\\hline \text { Cr. Office Supplies } & \\\text { Expense } & 3,480 \\\hline\end{array}$$
D) $$\begin{array} { | c | c | } \hline \text { Dr. Office Supplies } & 720 \\\hline \text { Cr. Office Supplies } & 720 \\ \text { Expense } & \\\hline\end{array}$$