The correct answer is option 1, Agriculture. The backbone of the Indus Economy was primarily dependent on agriculture. The Indus Valley Civilization, also known as the Harappan Civilization, was an ancient civilization that flourished around the Indus River in present-day India and Pakistan.

Agriculture played a significant role in the economy of the Indus Valley Civilization. The people of this civilization were skilled in cultivating crops, such as wheat, barley, rice, and various vegetables. The fertile land along the Indus River provided abundant water for irrigation and farming.

Although trade and commerce were also essential parts of the Indus economy, agriculture formed the foundation for the society. The surplus food production from agriculture allowed for the growth of urban centers and facilitated trade with other regions. Therefore, option 1, Agriculture, was the backbone of the Indus Economy.