In the pre-independence period, most manufacturing units were located in places suitable for overseas trade like Mumbai, Kolkata, Chennai, etc. The reason was to reduce the cost of ​manufacturing (due to low transportation costs to bring-in raw materials) and transportation from manufacturing units to seaport.

Z BECAUSE THE ALL ARE SEA PORTS FROM HERE THE GOOD WERE EASY TO TRANSPORT BY THE BRITISH

Explanation:

In the pre-independence period, most of the manufacturing units were located in Mumbai, Kolkata, and Chennai. Let's understand why these cities were the major centers of manufacturing during that time.

Mumbai:
1. Mumbai, formerly known as Bombay, was a major industrial and commercial center during the pre-independence period.
2. It had a well-developed port, which facilitated trade and transportation of goods.
3. Mumbai had a diverse industrial base, including textile mills, engineering industries, and chemical factories.
4. The presence of skilled labor, availability of raw materials, and access to markets made it an attractive location for manufacturing units.

Kolkata:
1. Kolkata, the capital of British India until 1911, was a major industrial hub during the pre-independence period.
2. It was strategically located near the Ganges River, which facilitated transportation of goods.
3. Kolkata was known for its jute mills, as the city had easy access to raw jute from Bengal's fertile lands.
4. Other industries such as iron and steel, cotton textiles, and coal mining also thrived in Kolkata.
5. The city had a large population, providing a steady supply of labor for the manufacturing units.

Chennai:
1. Chennai, formerly known as Madras, was another important manufacturing center during the pre-independence period.
2. It had a well-established textile industry, with several mills producing cotton textiles.
3. Chennai also had a significant presence of engineering and automobile industries.
4. The city had access to a natural harbor, facilitating trade and export of manufactured goods.
5. The availability of skilled labor, raw materials, and infrastructure made Chennai an attractive location for manufacturing units.

Conclusion:
In summary, Mumbai, Kolkata, and Chennai were the major centers of manufacturing in the pre-independence period due to factors such as access to ports, availability of skilled labor, presence of raw materials, and proximity to markets. These cities played a crucial role in the industrial development of India during that time.