Here below my VERY humble opinion (I only got 85% in Perf) ...
Q1)
Thrust = Mass x Acceleration = Volume x Density x (Vout-Vin)
As you can see the thrust is proportional to the density of the air for the same exhaust pipe air speed minus compressor intake.
The Density is also proportinal to the Pressure of the air and inversely proportional to the temperature.
Conclusion : Answer B
Q2)
The highest IAS can be reached at maximum output power from your engine. At high altitudes the output power of a piston engine reduces due the low air density.
Conclusion : Answer A
Q3)
I don't see the anwers proposed but I would say that the specific range increases. I don't remember the Fuel/Time ration but I guess that it is something like pounds/hour. Maximum endurance would minimize Fuel/Time but Maximum Range would have a higher Fuel/Time than Maximum Endurance.
Conclusion : Both increase