The correct answer is: A. Yamunanagar
The Yamuna river enters Haryana from the district of Yamunanagar. It flows through the districts of Kurukshetra, Karnal, Panipat, Sonipat, and Faridabad before entering Delhi. The Yamuna is a major tributary of the Ganges river. It is the longest river in India after the Ganges and the Brahmaputra. The Yamuna is a sacred river for Hindus and is worshipped by them.
Option B: Kaithal is a district in the Indian state of Haryana. It is located in the northern part of the state. The Yamuna river does not flow through the district of Kaithal.
Option C: Bhiwani is a district in the Indian state of Haryana. It is located in the southern part of the state. The Yamuna river does not flow through the district of Bhiwani.
Option D: Karnal is a district in the Indian state of Haryana. It is located in the northern part of the state. The Yamuna river flows through the district of Karnal. However, it does not enter Haryana from the district of Karnal. The Yamuna enters Haryana from the district of Yamunanagar.