The correct answer is (b) Bhagirathi.
The Kedarnath Ecodisaster of June 2013 was caused due to flash floods in the river Bhagirathi. The floods were caused by a cloudburst in the Kedarnath area, which led to heavy rains and landslides. The floods caused widespread damage to the Kedarnath temple complex and other infrastructure in the area. They also caused the deaths of over 10,000 people.
The Yamuna is a river in northern India. It is the longest tributary of the Ganges River. The Kosi is a river in eastern India. It is the largest tributary of the Ganges River. The Mandakini is a river in Uttarakhand, India. It is a tributary of the Alaknanda River, which is a tributary of the Ganges River.
The Yamuna, Kosi, and Mandakini are all important rivers in India. They are all sources of water for irrigation and drinking water. They are also important for transportation and fishing. However, they are also prone to flooding. The floods can cause damage to infrastructure and loss of life.