Refer to figures.
Note: We are not sure how pedantic the examiner wishes to be here. If they are favouring real life, one answer is correct, but if they are being very pedantic about "exact theory" then the answer could be a different one. We have gone with the ‘real life’ answer initially as this seems most likely, but please let us know if you have any information from the real exam that does not support this assumption, thank you!

Fixed pitch propellers are most efficient at a certain TAS value (for a certain RPM - which we are assuming), as this is where the angle of attack of the incoming airflow is the optimum angle of attack (similar to how a wing has an optimum angle of attack), where the lift to drag ratio is highest, to provide the most thrust for the least backwards torque on the engine. This can severely limit the cruise speed of aircraft with fixed pitch props, and therefore, aircraft are equipped with different pitch props based on their expected use-cases. slow training aircraft are equipped with fine pitch "climb" propellers and cruise focussed aircraft are equipped with coarser "cruise" propellers, so they are most capable in their expected speed range.

Constant speed (variable pitch) propellers do not have the same disadvantages, as they can change their blade angle to have a much greater band of maximum efficiency. They will therefore be fine for take-off and low speeds, but the constant speed unit will increase the blade angle to keep it more efficient at higher true airspeeds.

Therefore, when brakes are released on take-off, the propeller starts getting more efficient as it accelerates, until the propeller angle of attack reaches its optimum, and then after that, the propeller can be made to stay at optimum efficiency after this, in the climb and up to a much higher cruise TAS.

The only problem here is that the graph above shows the "optimum" band as being not quite level. This is the case due to a few factors, such as the propeller twist being optimum at a certain speed, etc., but we think that this small effect is not what the examiner is asking about, particularly for the speed range discussed in the question.