The correct answer is: C. 638 km
The Damodar River is a river in eastern India. It is the principal tributary of the Hooghly River, which in turn is a major tributary of the Ganges River. The Damodar River is 638 kilometers (396 mi) long and drains an area of 24,400 square kilometers (9,400 sq mi). The river originates in the Chhotanagpur Plateau in Jharkhand state and flows eastward through West Bengal state before joining the Hooghly River near Kolkata. The Damodar River is a major source of irrigation and hydroelectric power in eastern India. The river is also a major transportation route.
Option A is incorrect because the total length of the Damodar River is 638 kilometers, not 500 kilometers.
Option B is incorrect because the total length of the Damodar River is 638 kilometers, not 592 kilometers.
Option D is incorrect because the total length of the Damodar River is 638 kilometers, not 699 kilometers.