A crescendo of metallic thuds arose from the market, where the iron-smiths were ...... the pieces of metals.

Solution (By Examveda Team)

A crescendo of metallic thuds arose from the market, where the iron-smiths were hammering the pieces of metals.
In this context, "hammering" is the most appropriate verb to describe the action of the iron-smiths working with metal pieces. "Hammering" specifically refers to the repeated striking of a metal object with a hammer, which aligns with the noise described in the sentence. Therefore, "hammering" is the correct choice to complete the sentence, accurately conveying the action being performed by the iron-smiths.