| What is the main underlying operating principle of the Very-high-frequency Omnidirectional Range (VOR) aircraft navigational system? |
| A) A definite amount of time is required to send and receive a radio signal. |
| B) The difference between the peak values of two DC voltages may be used to determine an aircraft's altitude above a selected VOR station. |
| C) A phase difference between two AC voltages may be used to determine an aircraft's azimuth position in relation to a selected VOR station. |
| D) A phase difference between two AC voltages may be used to determine an aircraft's distance from a selected VOR station. |
