A clean way to remember this is to line up the three joining processes by temperature. Soldering uses filler that melts below 450°C. Welding melts the actual base metal, so it needs temperatures at or above the base metal's own melting point. Brazing sits in between these two: its filler must melt above 450°C so it is not classed as soldering, yet it must stay below the base metal's melting point so the parent material never turns liquid and its microstructure is left undisturbed. That upper boundary of 450°C is what officially separates brazing from soldering, so the answer is option (A), above 450°C.