How can you signal your intention to overtake outside a built-up area?

A)With the dipped or full beam lights, only.
B)With acoustic signals, exclusively.
C)With optical and acoustic signals.Correct
The intention to overtake the driver of the vehicle ahead may be signalled with optical or light signals, using the dipped beam, main beam, or both alternately, at very short intervals and in a way that avoids dazzling, and with acoustic signals, the horn. Depending on where we are, one method or another may be used:
-On interurban roads: acoustic signals (horn) or light signals (flashes or bursts).
-On urban roads: light signals (flashes or bursts). Horn prohibited.
-On interurban roads: acoustic signals (horn) or light signals (flashes or bursts).
-On urban roads: light signals (flashes or bursts). Horn prohibited.