Final answer:
The horizontal axis of the SPR trace should be labeled with appropriate units. The trace rises when the amount of dissolved solid increases over time. The trace falls when the amount of dissolved solid decreases over time.
Step-by-step explanation:
(a) The horizontal axis of the SPR trace should be labeled with the appropriate units. The units will depend on the specific context of the SPR trace. For example, if the SPR trace represents time on the horizontal axis, the units could be seconds, minutes, or hours.
(b) When the trace is slowly rising, it indicates that the amount of dissolved solid is increasing over time. This could be due to factors such as a reaction taking place or an increase in the solubility of the solid in the solution.
(c) When the trace is slowly falling, it indicates that the amount of dissolved solid is decreasing over time. This could be due to factors such as the precipitation of the solid or a decrease in the solubility of the solid in the solution.
(d) To redraw the part of the SPR trace marked with (*) to make it consistent with a smaller value of Kd, you would need to adjust the y-axis values of the trace to reflect the decrease in the amount of dissolved solid. This would result in a lower curve on the graph.