The correct answer is D, as Earth's largest inland lake is the Caspian Sea.
Caspian Sea is a lake of brackish water that extends between Europe and Asia. Its surface is 371,000 km², its average depth is 170 m, the maximum is 995 m and it is the largest lake in the world. Its dimensions are 1210 km in a north-south direction and 210 km to 436 km in an east-west direction.
It is mainly fed by the Volga River and by others less abundant like the Ural, the Emba and the Kura.