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The road users are obliged to notify the administrator of the public road or the nearest police unit when they are aware of the existence on the road of an obstacle or any other dangerous situation for the fluidity and safety of traffic. It is not mandatory to emit acoustic signals or to signal the road users who travel from the opposite direction.

The correct answer is: C

Recommendations:

Obligations and prohibitions of the drivers of vehicles during travel - Audio-Video Lesson --> Road Traffic Code - Obligations, prohibitions and aggressive driving

For answers  A  and  B 

Regulation** - Article 112

The drivers of vehicles signal with light, sound or arm warning means, as appropriate, before performing any maneuver or for avoiding an immediate danger.

Regulation** - Article 113

(1) The sound warning means must be used from a distance of at least 25 m from those they are addressed to, for a duration that ensures the perception of the signal and without causing them to perform maneuvers that may endanger traffic safety.
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For answer  C 

Regulation** - Article 96

(1) The road users are obliged to notify the administrator of the public road or the nearest traffic police officer when they are aware of the existence on the road of an obstacle or any other dangerous situation for the fluidity and safety of traffic.
(2) Is prohibited the any person to throw, leave or abandon objects, materials or substances or to create obstacles on the public road. The person who could not avoid creating an obstacle on the public road is obliged to remove it and, if this is not possible, to signal its presence and to immediately notify the administrator of the public road and the nearest police unit.

** Regulation = REGULATION for the application of OUG 195/2002 updated (Road Traffic Code Regulation)