Explanation:

The lake that differs from the rest in the group is The Guru Gobinda Sagar. Let's discuss each of the lakes mentioned in the options to understand why Guru Gobinda Sagar is different.

The Dal Lake:
1. The Dal Lake is located in Srinagar, Jammu, and Kashmir.
2. It is a famous tourist destination and is known for its scenic beauty.
3. The lake is surrounded by mountains and is famous for its houseboats and shikaras.
4. It is also the second-largest lake in Jammu and Kashmir.

The Nainital Lake:
1. The Nainital Lake is located in Nainital, Uttarakhand.
2. It is a natural freshwater lake and is a popular tourist attraction.
3. The lake is surrounded by hills and offers boating facilities to visitors.
4. It is also known as the Naini Lake and is one of the four lakes in Nainital.

The Bhimtal Lake:
1. The Bhimtal Lake is located in Bhimtal, Uttarakhand.
2. It is a picturesque lake surrounded by mountains and lush greenery.
3. The lake is named after Bhima, one of the Pandavas from the Hindu epic Mahabharata.
4. It is the largest lake in the Kumaon region and offers boating and fishing opportunities.

The Guru Gobinda Sagar:
1. The Guru Gobinda Sagar, also known as the Govind Sagar Lake, is located in Himachal Pradesh.
2. It is a man-made reservoir formed by the Bhakra Dam on the Sutlej River.
3. The lake is situated at a height of 518 meters and has a storage capacity of 9.34 billion cubic meters.
4. It is primarily used for irrigation, hydroelectric power generation, and drinking water supply.

Difference:
The main difference between Guru Gobinda Sagar and the other lakes is that it is a man-made reservoir formed by a dam, whereas the rest of the lakes mentioned are natural lakes. Guru Gobinda Sagar serves multiple purposes like irrigation, power generation, and water supply, unlike the other lakes, which are primarily tourist attractions.