What does a triangular vertical road sign with a white background and a red border signify in the Angolan traffic signaling system?

1. A danger warning sign (Sinal de Perigo), alerting drivers to an upcoming road hazard
2. A mandatory instruction sign (Sinal de Obrigação), ordering drivers to perform a specific action
3. A prohibitory sign (Sinal de Proibição), indicating a forbidden maneuver or restriction
4. An informative guide sign (Sinal de Indicação), indicating services or public utilities