ANS:C - both (a) & (b).

Brazing is indeed the process of joining metals by using a non-ferrous filler metal that melts at a temperature above 450°C (842°F) but below the melting point of the base metals being joined. So, the correct option is: both (a) & (b). Explanation:

• Without melting the base metal: Brazing allows the joining of metal parts without melting the base metals. Instead, the filler metal is heated to its melting point and then flows between the closely fitted surfaces of the joint by capillary action. The base metals remain in solid form during the brazing process.
• With a non-ferrous filler: Typically, brazing employs a filler material that is different from the base metals being joined. This filler metal, often an alloy of copper, silver, or other non-ferrous metals, melts at a lower temperature than the base metals but still provides a strong bond once solidified.