Explanation: Secondary activities add value to natural resources by transforming raw materials into valuable products.

• Cotton in the boll has limited use but after it is transformed into yarn, becomes more valuable and can be used for making clothes.
• Iron ore, cannot be used; directly from the mines, but after being converted into steel it gets its value and can be used for making many valuable machines, tools, etc.
• The same is true of most of the materials from the farm, forest, mine and the sea.
• Secondary activities, therefore, are concerned with manufacturing, processing and construction (infrastructure) industries.

Source: NCERT