Specialized drills have been found at the archaeological sites of Lothal and Chanhudaro, which were both important centers of the Harappan civilization. These specialized drills are significant archaeological discoveries because they provide insights into the technological advancements and craftsmanship of the people of the Harappan civilization. These drills were used for various purposes, including perforating beads and making holes in various materials, indicating the sophistication of their tools and techniques.

So, the correct option is [2].