The correct answer is option 'C' - Iron and steel industry.

Explanation:

The iron and steel industry is considered the base of all other industries due to its significant role in providing raw materials for various sectors. This industry is responsible for the production of iron and steel, which are essential materials used in the construction, manufacturing, and infrastructure development of almost all other industries.

1. Raw Material Provider:
The iron and steel industry supplies raw materials like iron ore, coal, and limestone, which are crucial for the production of steel. These materials are obtained through mining and extraction processes. Without a steady supply of these raw materials, many other industries would struggle to function efficiently.

2. Infrastructure Development:
The iron and steel industry plays a crucial role in infrastructure development. It provides the necessary materials for constructing buildings, bridges, roads, railways, and other essential structures. Without a robust iron and steel industry, infrastructure development would be hindered, affecting the growth and progress of other sectors.

3. Manufacturing Sector:
Numerous industries rely heavily on steel for their manufacturing processes. Steel is a versatile material with various applications, such as automobile manufacturing, machinery production, appliance production, and shipbuilding. The iron and steel industry acts as a backbone for these manufacturing sectors by providing high-quality steel for their production needs.

4. Construction Industry:
The construction industry heavily relies on iron and steel for its projects. From skyscrapers to residential buildings, steel is a vital component in the construction process. It provides strength, durability, and flexibility to structures, making them safer and more resilient. Without the iron and steel industry, the construction industry would struggle to meet the demands of urbanization and infrastructure development.

5. Economic Growth:
The iron and steel industry is a significant contributor to economic growth and employment generation. It creates job opportunities not only within the industry itself but also in related sectors like mining, transportation, and manufacturing. The growth of other industries is closely linked to the performance of the iron and steel industry, making it a critical sector for overall economic development.

In conclusion, the iron and steel industry serves as the base of all other industries by providing essential raw materials, supporting infrastructure development, and enabling manufacturing processes. Its importance in various sectors makes it a fundamental industry that impacts the overall economic growth of a country.