Final answer:
OAT gauges on faster aircraft will result in a warmer reading due to increased air compression, as the compression causes air molecules to move more rapidly, generating heat.
Step-by-step explanation:
The question concerns the Outside Air Temperature (OAT) gauges on faster aircraft and their readings due to air compression. The correct answer is A) Warmer; increased air compression. As an aircraft's speed increases, the air in front of the aircraft is compressed. This compression increases the temperature of the air because the molecules are forced closer together, causing them to move more rapidly which generates heat. This is similar to hot air being less dense because the components are moving more rapidly, as mentioned in part 'c' of the reference information.