Option 1: The Poetry - This option does not indicate commercial and economic development. Poetry is a form of art and does not directly relate to economic activities or trade.

Option 2: Scales - This is the correct answer. Scales were used for weighing goods during trade and commerce, indicating the presence of commercial activities in the Indus Valley civilization. The presence of scales suggests that the civilization had a system for measuring and managing goods and resources.

Option 3: The Boats - While boats were an important mode of transportation in the Indus Valley, their presence alone does not necessarily indicate commercial and economic development. Boats can be used for various purposes other than trade.

Option 4: The Houses - The presence of houses does not directly indicate commercial and economic development. Houses are a basic necessity for any civilization and do not provide specific evidence of economic activities.