A check dam is a:

Check dams:

• A check dam is a small, sometimes temporary, dam constructed across a swale, drainage ditch, or waterway to counteract erosion by reducing water flow velocity. 
• Check dams themselves are not a type of new technology; rather, they are an ancient technique dating from the second century A.D.
•  Check dams are typical, though not always, implemented in a system of several dams situated at regular intervals across the area of interest

Functions:

• It can be designed to create small reservoirs.
• It is used for reducing the velocity of flow in the channel.
• It can counteract erosion.
• It can avoid silting.
• It can increase groundwater recharge.

Here option 2 & Option 4 can be correct, but most appropriate answer is option 2