This is another wonderful example of the ambiguous nature of many JAR exam questions.
Alex has interpreted the question as asking for the configuration that should be used. Using this interpretation he is quite correct. To maximise speed you must maximise thrust and minimise (coefficient of) drag.
Oxford and Mad Jock have taken the question more literally and considered the conditions that will exist when an aircraft is flying at its maximum speed. To do this they have considered the drag and thrust curves and examined the values of each at maximum speed. At this point the curves cross, so drag and thrust are equal and are both at their maximum values. Using this method minimum drag occurs at Vmd which is most certainly not maximum speed.
If we wanted we could look a little deeper and find even more problems. Thrust from a propeller is greatest before brake release and reduces as forward speed increases. So maximum thrust occurs when the aircraft is stationary on the ground. And thrust (for a given throttle setting) is minimum when forward speed is maximum. so for a prop aircraft we might conclude that at maximum forward speed the thrust is minimum and the drag maximum.
Personally I believe that Oxford and Mad Jock are correct. Unfortunately none of us have any way of knowing what the examiners think the correct answer is. Unless of course we could find a student who scored 100% in an exam in which this question apeared. (I'm not holding my breath here).
So if all of the students at OATS and all of the students at BGS (and any other school we might choose to name) remember exactly what they have been taught, some will get the marks and some will not!!!!!
This problem will be resolved only if all students finding this question in their exam challenge it on the basis of the above argument. They should then report the problem to their CGI, so that he can also callenge it.
A similar problem exists with questions relating to changing pitch angle in a glide. If the nose is already pointing down and we push it further down have we increased or decreased pitch attitude. The (conventional) answer to that question depends on which school you go to. But once again, only the examiners know what they accept as the correct answer.