In a graph of acceleration versus net force, the slope represents the inverse of the mass of the boat. This is based on Newton's second law of motion, which states that \( F = ma \) (force equals mass times acceleration). Rearranging the equation, you can express acceleration as \( a = \frac{F}{m} \). Thus, if you plot force (F) on the x-axis and acceleration (a) on the y-axis, the slope of the graph (change in acceleration/change in force) will equal the inverse of mass (\( \frac{1}{m} \)).
Therefore, the correct answer is:
the inverse of the mass of the boat.