Final answer:
The question is about the type of road sign indicating an obstruction or change in road alignment. Such signs are critical for driver awareness and road safety. 'Obstruction Ahead' or 'Curve Ahead' would be used depending on the specific road situation.
Step-by-step explanation:
The question asked is related to the types of road signs and what they indicate. If a sign is mounted immediately in front of an obstruction or at changes in road alignment, it typically means that a driver needs to be aware of a potential hazard or alteration in the path ahead. The correct answer from the provided options would generally be A. Obstruction Ahead or C. Curve Ahead, depending on the specific situation and the local traffic sign conventions. For example, if there is a sudden curve, the sign would be 'Curve Ahead,' but if there is an obstruction like roadwork or a fallen tree, the sign would state 'Obstruction Ahead.' Emphasizing caution and alertness in these scenarios is crucial for road safety.