The correct answer is: C. 12th century AD.
The Nirmand copper plates are a set of five copper plates that were found in the village of Nirmand in Himachal Pradesh, India. The plates are inscribed with a grant of land made by the ruler of the Western Chalukya dynasty, Vikramaditya VI, to a Brahmin named Vishnugupta. The plates are dated to the 12th century AD.
The plates are important because they provide evidence of the rule of the Western Chalukyas in the region. They also provide information about the social and economic conditions of the time. The plates are written in Sanskrit and Prakrit.
The plates are currently on display at the Archaeological Museum in Shimla, India.
Option A is incorrect because the Nirmand copper plates are dated to the 12th century AD, not the 7th century AD.
Option B is incorrect because the Nirmand copper plates are dated to the 12th century AD, not the 10th century AD.
Option D is incorrect because the Nirmand copper plates are dated to the 12th century AD, not the 15th century AD.