Introduction:
The question asks which one of the following lakes is not created by human beings. The options given are Gobind Sagar, Nizam Sagar, Barapani, and Hirakud. We need to identify the lake that is naturally formed and not created by human intervention.

Explanation:
- Gobind Sagar: Gobind Sagar is a reservoir located in the Indian state of Himachal Pradesh. It was created by the construction of the Bhakra Dam on the Sutlej River. The dam was built for hydroelectric power generation and irrigation purposes. Therefore, Gobind Sagar is a lake created by human beings.

- Nizam Sagar: Nizam Sagar is a reservoir located in the Indian state of Telangana. It was built across the Manjira River, a tributary of the Godavari River. The reservoir was constructed in the 1920s to provide irrigation water to the surrounding agricultural lands. Thus, Nizam Sagar is also a lake created by human beings.

- Barapani: Barapani, also known as Umiam Lake, is a reservoir located in the Indian state of Meghalaya. It was formed as a result of the damming of the Umiam River for the purpose of generating hydroelectric power. The lake is a popular tourist destination and also serves as a source of drinking water for the nearby city of Shillong. Therefore, Barapani is a lake created by human beings.

- Hirakud: Hirakud is a reservoir located in the Indian state of Odisha. It was constructed across the Mahanadi River and is one of the largest artificial lakes in Asia. The primary purpose of building the Hirakud Dam was to control floods in the Mahanadi basin and provide irrigation water to the surrounding farmlands. Thus, Hirakud is also a lake created by human beings.

Conclusion:
Among the given options, the lake that is not created by human beings is option C, Barapani. Gobind Sagar, Nizam Sagar, and Hirakud are all reservoirs created by the construction of dams for irrigation and power generation purposes. However, Barapani is a natural lake formed by the damming of the Umiam River.