The correct answer is (a) Sattal, Nainital.
The Himalayan Spice Garden is a botanical garden located in Sattal, Nainital district, Uttarakhand, India. It was established in 1998 by the Forest Research Centre, Haldwani. The garden is spread over an area of 10 hectares and houses a collection of over 100 species of spices, herbs, and medicinal plants. The garden is open to the public and is a popular tourist destination.
The other options are incorrect because:
(b) Pathri, Haridwar is a village in Haridwar district, Uttarakhand, India. It is located on the banks of the Ganges River. The village is known for its temples and shrines.
(c) Sauni, Ranikhet is a village in Almora district, Uttarakhand, India. It is located in the Kumaon Himalayas. The village is known for its scenic beauty and its apple orchards.
(d) Vikasnagar, Dehradun is a town in Dehradun district, Uttarakhand, India. It is located on the banks of the Yamuna River. The town is known for its educational institutions and its industries.