The discovery of spindle whorls in Harappan sites suggests that the inhabitants were engaged in:

The correct option is

Spinning of thread

Explanation

Archaeological excavations in the Indus Valley Civilization have yielded specific artifacts that provide insight into the domestic and industrial activities of the period. Spindle whorls are key indicators of textile production technology.

Analysis:

• Nature and Function: A spindle whorl is a disc-shaped or spherical object with a central hole, designed to be fitted onto a spindle. It acts as a weight or flywheel to maintain the momentum of the spin, facilitating the twisting of fibers into thread.
• Archaeological Evidence: Numerous spindle whorls made of terracotta, faience, and shell have been discovered across various Harappan sites. This widespread availability suggests that the spinning of thread (cotton and wool) was a common craft, likely practiced at the household level.
• Comparison with other options:
  • Pottery making utilizes a potter's wheel, which is distinct in size and mechanism.
  • Metal casting relies on crucibles and moulds.
  • Bead drilling utilizes specialized drills (such as those found in Chanhudaro and Lothal), not whorls.

Key Takeaway: Spindle whorls are the primary archaeological evidence for the practice of spinning thread and the existence of a developed textile industry in the Indus Valley Civilization.