Explanation:

(a) Rohtang Pass* - is a high mountain pass on the eastern Pir Panjal Range of the Himalayas around 51 km (32 mi) from Manali. It connects the Kullu Valley with the Lahaul and Spiti Valleys of Himachal Pradesh, India.
(b) Kunzum Pass - is a high mountain pass on the eastern Kunzum Range of the Himalayas some 122 km (76 mi) from Manali. It connects the Kullu Valley and Lahaul Valley with the Spiti Valley of Himachal Pradesh, India. It is on the route to Kaza the subdivisional headquarters of Spiti. There is also a 9 km trek to the Moon Lake of the Chandratal from the Kunzum Pass.
(c) Borasu Pass -  is a high mountain pass in the Himalaya Mountains of Himachal Pradesh in the India. The pass is located on the border of Uttarakhand and Himachal Pradesh near the border with Tibet. It was an ancient trade route between Har ki Doon valley and Kinnaur valley.
(d) Chanhal Pass - links Dodra Kwar and Rohru (Chirgaon) in the Shimla district of Himachal Pradesh, India. The pass sits atop the Chanshal Peak, which at 4,520 metres (14,830 ft) and is thus the highest peak in the Shimla district. The pass remains open from May to October and is covered with snow for the rest of the year.