Hey Cron
OK, I'll give it a go. First off, this is translational lift, not effective translational lift, so we're talking about performance increases as a result of some wind going over the rotor system as opposed to the surge you feel at 16-24kts. Think of a zero wind hover compared to a hover in a 10kt wind; you will use less power in the 10kt hover even though you're still well below ETL.
The reason we get the performance increase is because there has been a change in the angle the air enters the rotor system. It's no longer being drawn exclusively from above, it's now getting some 'help' from wind which is coming into the rotor system in the same plane as the rotor system.
When you draw this out as a vector diagram you can now split the airflow through the rotor system into two components. Given the same downwash (i.e. the same mass flow rate of air), what you find is that the helicopter's forward movement has increased the component of airflow in the plane of the rotor system and that has led to a reduction in the required airflow perpendicular to the rotor system. The word we use to describe airflow perpendicular to the rotor system is 'induced flow'.
Bear with me - that's the tricky step out of the way, it's all downhill from here!
We know that induced flow is a bad thing because higher induced flow means lower angle of attack for the blades. Do you remember the vector diagram with rotational relative wind, induced flow, resultant relative wind, chord line, pitch angle and angle of attack? - v important that one, memorise if you don't know it - just keep drawing it out until you have it. You can use it again and again to describe IGE/OGE, inflow roll, retreating blade stall etc.
So reducing induced flow is officially "a good thing" because it leads to an increased angle of attack for the blades.
In the question it talks about forward movement of cyclic leading to increased angle of attack. That's why I favoured answer c.
I think what this question is driving at is that translational lift is more to do with the increased 'bite' that the blades get on the air due to reduced induced flow than due to increased mass flow rate.
At least that's my take on it, not sure if that helps. I had to teach aerodynamics as part of working a CFI but I seldom got into this much depth apart from with my very best students.
Kris