2. What is the predominant material of the exterior walls? (expanded)
[] 1 Cement block, brick, stone, finished wood
[] 2 Clay brick, adobe, cane/mud
[] 3 Rough wood, boards, plywood
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[] 4 Prefabricated material
[] 5 Bamboo, cane, thatch
[] 6 Zinc, fabric, cardboard, cans, discarded materials, plastics
[] 7 Without walls