The total earnings of the salesman can be expressed as \( 2000 + 0.1s \), where \( 2000 \) is a fixed amount added to the earnings from commissions. This indicates that \( 2000 \) is not dependent on the sales amount \( s \).
Since \( 2000 \) is added to the earnings derived from the sales, it represents the base salary of the salesman. The commission, which is \( 0.1s \), is the additional earnings based on his sales.
Therefore, \( 2000 \) represents the salesperson's monthly base salary.
The correct option is:
A. his monthly base salary in dollars