When extreme temp,must be consided in selecting the material for valves the best choice is what? BRONZE,CARBON STEEL,COPPER,IRON

Is this a test question?

when extreme temp,must be consided in selecting the material for valves the best choice is what? BRONZE,CARBON STEEL,COPPER,IRON
What kind of temperature are we talking about? How much pressure? My first choice would be brass. Regards, Tom