The correct answer is: Uttarakhand.
Himachal Pradesh is a state in northern India. It is bordered by Jammu and Kashmir to the north, Ladakh to the northeast, Uttarakhand to the east, Uttar Pradesh to the south, Haryana and Punjab to the southwest, and the Indian state of Jammu and Kashmir to the west.
Uttarakhand is a state in northern India. It is bordered by Himachal Pradesh to the north, Uttar Pradesh to the east, Madhya Pradesh to the southeast, Rajasthan to the southwest, and Haryana and Delhi to the west.
Haryana is a state in northern India. It is bordered by Punjab to the west, Himachal Pradesh to the north, Uttarakhand to the northeast, Uttar Pradesh to the east, Rajasthan to the south, and Delhi to the southwest.
Punjab is a state in northern India. It is bordered by Haryana to the west, Himachal Pradesh to the north, Jammu and Kashmir to the northeast, Uttarakhand to the east, Uttar Pradesh to the south, and Rajasthan to the southwest.
Therefore, the only option that borders Himachal Pradesh to the south is Uttarakhand.