Final answer:
The 'diamond' shape sign on the road is used to warn of existing or possible hazards on the road. It alerts drivers to be cautious and aware of any potential dangers that may be present.
Step-by-step explanation:
The 'diamond' shape sign on the road is used to warn of existing or possible hazards on the road. It alerts drivers to be cautious and aware of any potential dangers that may be present. These hazards could include sharp turns, road work zones, slippery roads, or any other condition that may require drivers to take extra precautions. Therefore, option (c) 'To warn of existing or possible hazards on the road' is the correct answer.