Final answer:
Protective grounds are designed to safeguard line workers from electrical shock and arc flash, encompassing both thermal and shock hazards.
Step-by-step explanation:
Protective grounds protect the line worker from the hazards of electrical shock and arc flash. Therefore, the answer to the question is c. Both a and b. Electrical safety systems and devices are designed to mitigate the risks associated with thermal hazards and shock hazards. Thermal hazards result from excessive electric power, such as starting a fire, while shock hazards occur when electric current passes through a person, with varying degrees of severity. Awareness and prevention of these hazards are crucial for safety in environments where electrical systems are being serviced.