The correct option is Plain pottery.
Explanation
The pottery of the Indus Valley Civilization is primarily wheel-made, with hand-made examples being rare. The ceramic finds are broadly categorized into plain pottery and painted pottery based on surface treatment and decoration.
- Plain Pottery: This category constitutes the majority of the pottery found at Harappan sites. It is typically made of red clay, with or without a fine red or grey slip. It includes varieties such as knobbed ware, which is ornamented with rows of knobs. These vessels were predominantly used for utilitarian purposes, such as the storage of grains and water.
- Painted Ware: Also referred to as Red and Black ware, this category is less common than plain pottery. It features a red slip background with designs painted in black, depicting geometric patterns, vegetation, and animals.
- Polychrome Pottery: This type is rare and typically comprises small vases decorated with geometric patterns in red, black, and green, occasionally with white and yellow accents.
- Glazed Ware: While the Harappans produced faience, true glazed pottery is extremely rare in the Indus Valley context.
Key Takeaway: Although the painted Red and Black ware is artistically significant, plain pottery forms the bulk of the ceramic assemblage in the Indus Valley Civilization.