The correct answer is: All of these.
Gurugram, Rewari, and Mahendragarh are all districts in Haryana, India, that are located in the northwestern part of the state. The northwestern part of Haryana is characterized by undulating sandy plains. These plains are part of the Indo-Gangetic Plain, which is a vast plain that stretches across northern India and Pakistan. The Indo-Gangetic Plain is one of the most fertile regions in the world, and it is home to a large population of people.
The undulating sandy plains in Haryana are a result of the deposition of sand by the rivers that flow through the region. The rivers, such as the Yamuna and the Ghaggar, carry sand from the Himalayas and deposit it on the plains. The sand is then blown by the wind, which creates the undulating hills that are characteristic of the region.
The undulating sandy plains in Haryana are a popular tourist destination. The plains are home to a variety of wildlife, including deer, rabbits, and birds. The plains are also home to a number of historical sites, such as the ancient city of Mahendragarh.