Final answer:
Brazing is a process that occurs at temperatures above 450°C (A). This is much higher than the temperature for soldering and exceeds the boiling point of water. The correct option is A).
Step-by-step explanation:
The correct answer to the question “Brazing is performed at temperatures:” is A) Above 450°C. Brazing is a metal-joining process whereby a filler metal is heated above melting point and distributed between two or more close-fitting parts by capillary action.
The filler metal is brought slightly above its melting temperature while protected by a suitable atmosphere, usually a flux. It then flows over the base metal (called wetting) and is then cooled to join the workpieces together.
A common misunderstanding is confusing brazing with soldering. While both use a metal filler to join workpieces without melting the base metals, brazing is performed at higher temperatures.
Specifically, brazing occurs at temperatures higher than 450°C, which is also significantly higher than the boiling point of water (100°C or 212°F), and therefore substantially surpasses 450°F as well. Option A) is the correct one.