Context:
The question is related to the historical figure Kumardevi, who was the Queen of Govinda Chandra Gahadavala. The question asks about a vihar (monastery) constructed by Kumardevi. The options provided are Bodhgaya, Kushinagar, Kanauj, and Sarnath. The correct answer is Sarnath.

Explanation:
1. Sarnath:
Sarnath is a significant Buddhist pilgrimage site located near Varanasi in Uttar Pradesh, India. It is known for being the place where Gautama Buddha first taught the Dharma after attaining enlightenment. Sarnath is considered one of the four main pilgrimage sites associated with the life of Buddha.

2. Construction of Dharmachakra-jina-vihar:
Kumardevi, the Queen of Govinda Chandra Gahadavala, constructed a vihar called Dharmachakra-jina-vihar in Sarnath. A vihar is a Buddhist monastery or dwelling place for monks. The Dharmachakra-jina-vihar is significant as it represents the teachings of Buddha and serves as a place for Buddhist practitioners to gather and study the Dharma.

3. Significance of Sarnath:
Sarnath holds great historical and religious importance in Buddhism. Here are some key points about its significance:

- First Sermon: Sarnath is the place where Gautama Buddha delivered his first sermon, known as the Dhammacakkappavattana Sutta or "Setting in Motion the Wheel of Dharma." In this sermon, Buddha explained the Four Noble Truths and the Eightfold Path, which form the foundation of Buddhist teachings.

- Deer Park: Sarnath is also referred to as Deer Park, as it was a deer reserve during Buddha's time. It was here that Buddha encountered his first five disciples, who later became his first followers.

- Ashoka's Patronage: The Mauryan Emperor Ashoka played a significant role in promoting Buddhism and its sites of importance. Ashoka visited Sarnath and constructed several stupas and monasteries to commemorate Buddha's teachings. The Dharmachakra-jina-vihar may have been one of the structures built during this period.

Conclusion:
In conclusion, Kumardevi, the Queen of Govinda Chandra Gahadavala, constructed the Dharmachakra-jina-vihar in Sarnath. Sarnath is a significant Buddhist pilgrimage site where Gautama Buddha delivered his first sermon and is associated with various historical events in Buddhism. The Dharmachakra-jina-vihar represents the teachings of Buddha and serves as a place for Buddhist practitioners to gather and study the Dharma.