The expression for the salesman's total earnings is given as \(2000 + 0.1s\) dollars, where \(s\) represents the total sales in dollars.
In this equation:
- The term \(2000\) is a fixed amount that does not depend on sales.
- The term \(0.1s\) represents the commission, which is 10% of the sales.
Thus, the \(2000\) in the equation represents the base salary that the salesman earns each month, regardless of his sales.
Therefore, the correct answer is:
A. his monthly base salary in dollars