The correct answer is A. Yamunanagar.
Yamunanagar district has the maximum area under reserved forests in the state of Haryana. The total area of reserved forests in Yamunanagar district is 1,200 square kilometers. The main reserved forests in Yamunanagar district are the Asan Barrage Forest, the Bhakhra Dam Forest, and the Jagadhri Forest.
The Asan Barrage Forest is located on the banks of the Yamuna River. It is a popular tourist destination and is home to a variety of wildlife, including tigers, leopards, and deer. The Bhakhra Dam Forest is located on the banks of the Sutlej River. It is a popular spot for fishing and boating. The Jagadhri Forest is located near the city of Jagadhri. It is a popular spot for hiking and camping.
The other options are incorrect because they do not have the maximum area under reserved forests in the state of Haryana. Panchkula district has a total area of reserved forests of 800 square kilometers. Kaithal district has a total area of reserved forests of 600 square kilometers. Kurukshetra district has a total area of reserved forests of 400 square kilometers.