Final answer:
A welding arc can reach temperatures of around 20,000 degrees Celsius, which is necessary for melting and fusing materials in welding applications.
Step-by-step explanation:
The temperatures involved in welding are extremely high and are a critical aspect of the process. In the context of the welding arc temperatures, option b) 20,000 degrees Celsius is the accurate choice. A welding arc can indeed reach these high temperatures, which are sufficient to melt various metals used in welding applications. Such intense heat is necessary to melt the electrode and fuse materials, creating a strong weld. Proper safety gear, such as a welder's gloves and helmet, is crucial due to the high temperatures and intense light produced during welding, which can cause skin burns and retinal damage if proper precautions are not taken.