Under what circumstance is sounding the acoustic warning device (buzina / sinal sonoro) permitted under Article 21 of the Angolan Highway Code?

1. Only in cases of imminent danger; additionally, outside localities, to warn another driver of the intention to overtake or at blind bends, junctions, and crests
2. Whenever greeting friends or passing familiar businesses
3. To encourage the vehicle ahead to move faster when a traffic light turns green
4. At all intersections regardless of visibility