Due to the reduced density of air at any altitude above sea level, to maintain the same IAS you will need to fly at a faster TAS, thus you will require more thrust, this will manifest itself by the need to increase power and push the throttle forward to maintain the same IAS. This can clearly be seen by refering to the basic thrust required graph, i.e as TAS increases more thrust is required. On this basis personally i would be selecting D.......
