| What is the main underlying operating principle of an aircraft's Distance Measuring Equipment (DME)? |
| A) A measurable amount of time is required to send and receive a radio signal through the Earth's atmosphere. |
| B) The difference between the peak values of two DC voltages may be used to determine an aircraft's distance to another aircraft. |
| C) A measurable frequency compression of an AC signal may be used to determine an aircraft's altitude above the earth. |
| D) A phase inversion between two AC voltages may be used to determine an aircraft's distance to the exit ramp of an airport's runway. |
