The correct answer is B. River.
A lotic system is a body of water that has a current, such as a river or stream. The current in a lotic system is caused by the flow of water from one place to another. The current in a lotic system can be strong or weak, depending on the size of the body of water and the slope of the land.
A pond is a body of water that is surrounded by land and has no current. The water in a pond is usually still or has a very slow current. Ponds are often used for recreation, such as fishing, swimming, and boating.
A lake is a large body of water that is surrounded by land. Lakes can be freshwater or saltwater. Lakes are often used for recreation, such as fishing, swimming, and boating.
A reservoir is a man-made lake that is created by damming a river. Reservoirs are used for a variety of purposes, such as water storage, flood control, and hydroelectric power generation.
In conclusion, the correct answer is B. River. A river is an example of a lotic system because it has a current.