Final answer:
The book value of the store equipment on December 31 is $11,500.
Step-by-step explanation:
To calculate the book value of the store equipment on December 31, we need to start with the original cost of the equipment and subtract the accumulated depreciation. The original cost of the equipment was $12,000. The depreciation for the month of December was $500. Therefore, the book value of the store equipment on December 31 would be $12,000 - $500 = $11,500.
So, the correct answer is A. $11,500.