Why is 'waste material' considered one of the best indicators of craftwork?

It suggests that craft production was taking place at various centres

The correct answer is Option 4 - It suggests that craft production was taking place at various centres

In order to identify centres of craft production, archaeologists usually look for the following: raw material such as stone nodules, whole shells, copper ore; tools; unfinished objects; rejects and waste material. In fact, waste is one of the best indicators of craft work.

For instance, if shell or stone is cut to make objects, then pieces of these materials will be discarded as waste at the place of production. Sometimes, larger waste pieces were used up to make smaller objects, but minuscule bits were usually left in the work area. These traces suggest that apart from small, specialised centres, craft production was also undertaken in large cities such as Mohenjodaro and Harappa.