Concept:An old river has a low gradient, slow flow, and deposits sediment to form flood plains, levees, and meanders.
Explanation:Waterfalls and rapids are typical of a young river, not an old one.
An old river flows sluggishly and develops pronounced meanders, so statement II is correct.
Fast flow and truncated spurs belong to a young or early mature river, so statement III is incorrect.
Levees and a flood plain are formed in the old stage of a river, so statement IV is correct.
Therefore, the valid features are statements II and IV only.
Answer:A. II and IV only