Introduction:
The construction of railways in India was a significant development during the British colonial period. The railways played a crucial role in connecting different regions of the country and facilitating transportation and trade. The construction of railways in India involved both private enterprises and state agencies. Option 'B' (1880) is the correct answer as it marks a significant period when private enterprise started taking an active role in railway construction.

Private Enterprise in Railway Construction:
Before the 1880s, railway construction in India was primarily carried out by state agencies like the East India Company and later the Indian Railways Department. However, after the 1880s, private companies were granted concessions to build and operate railways in India. This marked a shift towards involving private enterprise in railway construction.

Participation of Private Companies:
The participation of private companies in railway construction gained momentum during the late 19th century. These companies were granted concessions and licenses by the British government to build and operate railways in specific regions. They played a crucial role in extending the railway network to various parts of India.

Benefits of Private Enterprise:
1. Capital Investment: Private companies brought in substantial capital investment for railway construction. They had the financial resources to undertake large-scale projects and develop railway infrastructure.

2. Technical Expertise: Private companies often had access to advanced technology and expertise in railway construction. They introduced modern engineering techniques and equipment, leading to efficient and faster construction of railway lines.

3. Employment Opportunities: Railway construction by private companies created employment opportunities for the local population. This contributed to economic development and improved living standards in the regions where railways were built.

4. Increased Connectivity: The involvement of private companies in railway construction led to increased connectivity between different parts of India. It facilitated the transportation of goods, raw materials, and people, thus boosting trade and economic growth.

5. Revenue Generation: Private companies operated the railways as profit-oriented enterprises. The revenue generated from ticket sales and freight charges contributed to the overall economic development of the country.

Conclusion:
The construction of railways in India involved both state agencies and private enterprises. While state agencies initially played a dominant role, private companies started actively participating in railway construction from the 1880s onwards. This shift towards private enterprise brought in capital investment, technical expertise, employment opportunities, increased connectivity, and revenue generation. The railways built through private enterprise played a crucial role in transforming India's transportation infrastructure and fostering economic growth.