'Crime' is related to 'Police' in the sense of the authority or mechanism that controls, manages, or responds to it. In the same way, 'Flood' is related to which entity that is primarily used to control or contain it?

Introduction / Context:
Analogy questions test your ability to recognize relationships between pairs of words and then apply the same relationship to a new pair. Here, “Crime : Police” captures a control/containment or responsible-agency relation. We must pick what similarly relates to “Flood”.

Given Data / Assumptions:

• Crime is an undesirable event in society.
• Police are the designated authority to control, manage, and respond to crime.
• Flood is an undesirable hydrological event.
• We seek the device/agency primarily used to control or contain a flood.

Concept / Approach:
The mapping is “problem : controller/containing mechanism.” Police do not cause crime; they respond to and control it. For floods, structural flood-control works such as dams, embankments, and barrages are designed to restrain or regulate water to mitigate flooding. Among the options, “Dam” best mirrors “Police” in the role of controller/containment device.

Step-by-Step Solution:
1) Identify relation type in first pair: crime is controlled/managed by police.2) Transfer the relation to the second pair: flood is controlled/managed by what?3) Evaluate candidates for their primary role in flood control.4) Select the option that most directly functions as a flood-control mechanism: Dam.

Verification / Alternative check:
Ask whether each choice prevents or governs the phenomenon. A dam stores and regulates water flow, thereby reducing flood peaks. This aligns with the “control/containment” relation.

Why Other Options Are Wrong:

• Rain: This is a cause of flood, not a controller.
• River: A medium where flooding occurs; not a controlling agent.
• Reservoir: A stored body of water; may exist behind a dam but is not itself the control device.
• Relief camp: Addresses consequences after flooding, not control.

Common Pitfalls:
Confusing cause/effect items (rain, river) or after-the-fact responses (relief camp) with a controlling mechanism leads to incorrect mapping.

Final Answer:
Dam