The Guwahati Railway Station has become the first-ever railway station in the Indian Railways to get an ISO certification from the National Green Tribunal (NGT) for “providing passenger amenities in a clean and green environment.”The station also has amenities such as High-class reserve (VIP) lounge, waiting rooms, AC and non-AC retiring rooms, food courts and sanitation facilities.ISO stands for “International Organisation for Standardisation” that is responsible for establishing the standard in different areas of activities.Hence, the correct option is (b).