Concept:
Indian Railways is one of the world's largest rail networks. Its geography includes various gauges, zones, and massive engineering projects in difficult terrains like the Himalayas.
Step 1: Evaluating Statements A and B (Network Stats).
• Gauge (A): Due to Project Unigauge, Broad Gauge now accounts for over 90% of the total route length. Metre gauge is being phased out.
• Electrification (B): As of 2024, Indian Railways has achieved nearly 95% electrification of its broad gauge network, aiming for 100% shortly. The figure of 25% is outdated by several decades.
Step 2: Evaluating Statement C (Engineering).
The Udhampur-Srinagar-Baramulla Rail Link (USBRL) is a landmark project. A critical section of this line passes through the Pir Panjal Railway Tunnel (India's longest transport tunnel at approx. 11.2 km). This statement is correct.
Step 3: Evaluating Statement D (Zones).
Kolkata is unique as it serves as the headquarters for three different zones: Eastern Railway, South Eastern Railway, and Kolkata Metro. Thus, (D) is correct.
Step 4: Conclusion.
Only statements C and D are accurate in the current context.