Solution
This question is based on the old numbering of National Highways in India.
NH6 runs through Gujarat, Maharashtra, Chhattisgarh, Odisha, Jharkhand and West Bengal state in India.
National Highway 7 or NH 7, is major North-South National Highway in India that runs through the states of Uttar Pradesh, Madhya Pradesh, Maharashtra, Telangana, Andhra Pradesh, Karnataka, and Tamil Nadu.
National Highway 8 is the busiest highway in the subcontinent, as it connects the national capital Delhi to the financial capital Mumbai, as well as important cities Gurgaon, Jaipur, Ajmer, Udaipur, Ahmedabad, Vadodara and Surat.
NH 15 runs through Pathankot - Amritsar - Tarn Taran Sahib - Bhatinda - Ganganagar - Bikaner - Jaisalmer - Barmer - Samakhiali (Punjab, Rajasthan and Gujarat)
Hence, option C is the correct answer.