The assertion states that industries based on bulky, cheap, and weight-losing materials are located close to the raw materials. This is correct because such industries, like the cement industry, steel industry, and paper mills, need raw materials like limestone, coal, and timber, which are heavy and lose weight during processing. To minimize transportation costs, they are typically located near the source of these raw materials.
The reason for this proximity is to reduce transportation costs. When raw materials are bulky and weight-losing, it is essential for industries to be located close to the sources to prevent high transportation costs that would otherwise make the products expensive. Hence, the reason (R) correctly explains assertion (A).
Therefore, both (A) and (R) are true, and (R) is the correct explanation of (A).