In the use-based classification of the Index of Industrial Production (IIP), different weights are assigned to different categories of goods based on their contribution to the overall industrial production. The maximum weight is assigned to the category of primary goods.

Primary goods refer to raw materials or agricultural products that are directly extracted from nature and used in the production of other goods. Examples of primary goods are crude oil, coal, minerals, timber, etc.

Assigning the maximum weight to primary goods in the IIP classification indicates their significance in the overall industrial production. This implies that the production and performance of primary goods have a major influence on the overall growth and productivity of the industrial sector.

It is important to note that while the correct answer provided is option 1 (primary goods), it is always advisable to cross-check the information and verify the accuracy of the answer in case of any doubt or discrepancy.