When determining which joining operations do not involve melting the surfaces being joined, it's helpful to examine each option in detail:
Option A - Arc Welding: This method uses an electric arc to melt the metals at the joining point. Hence, both surfaces will experience melting.
Option B - Brazing: Brazing involves melting a filler metal, which has a lower melting point than the pieces being joined. The surfaces of P and Q are not melted; only the filler metal is. So, this method does not involve the melting of P and Q.
Option C - Adhesive Bonding: This technique uses an adhesive substance to bond surfaces together without melting them. Therefore, there is no melting of surfaces P and Q.
Option D - Spot Welding: Spot welding is a resistance welding process that involves the localized melting of the surfaces to be joined. Thus, surfaces P and Q are melted during this process.
Therefore, the correct joining operations where there is no melting of the two surfaces P and Q are:
Option B: Brazing
Option C: Adhesive bonding
