The correct answer is: A. Mahatma Gandhi bridge
The Mahatma Gandhi Setu, also known as the Patna Sahib Bridge, is a cantilever bridge over the Ganges River in Patna, India. It is the longest railway bridge in India and the second-longest cantilever bridge in Asia. The bridge was built between 1959 and 1965 and was opened to traffic in 1966. It is named after Mahatma Gandhi, the leader of the Indian independence movement.
The bridge is 5,575 meters long and has a main span of 1,500 meters. It is made of steel and concrete and has a total of 13 spans. The bridge is designed to withstand earthquakes and floods. It is a major transportation link between Patna and the rest of India.
The other options are incorrect because:
- Option B, Son bridge, is a bridge over the Son River in Bihar, India. It is not a railway bridge.
- Option C, Bagha-Chhitari bridge, is a bridge over the Ganges River in Bihar, India. It is not a railway bridge.
- Option D, Rajendra bridge, is a bridge over the Ganges River in Patna, India. It is a road bridge, not a railway bridge.