If the y-axis represents acceleration, the appropriate choice for the x-axis from the options provided would be force. This is based on Newton's second law of motion, which states that acceleration is directly proportional to force and inversely proportional to mass (F = ma).
Thus, if you were to plot a graph of acceleration (y-axis) versus force (x-axis), it would show how acceleration changes in relation to applied force, assuming mass remains constant. If mass varies, then you would need to adjust your graph accordingly, but with the options given, force is the most fitting for the x-axis.