Among the options given, the Himasagar Express (Jammu Tawi to Tirunelveli, approximately 3,700 km) is the longest-distance train. However, it's worth noting that the Vivek Express (Dibrugarh to Kanyakumari, 4,273 km) is actually India's longest train, but it's not among the options. The question asks for the longest 'covering' train among the given choices.