## Core Concept
The presence of amoebic cysts in water indicates contamination with *Entamoeba histolytica*, a protozoan parasite that can cause amoebiasis. Effective management of contaminated water involves ensuring the water is safe for consumption to prevent outbreaks of amoebiasis.

## Why the Correct Answer is Right
Chlorination of water is a widely accepted method for inactivating or killing *E. histolytica* cysts. The cysts are relatively resistant to environmental stresses but can be inactivated by chlorine doses that are slightly higher than those typically used for bacteria and viruses. This method is effective, practical, and commonly used in water treatment plants to ensure water safety.

## Why Each Wrong Option is Incorrect
- **Option A:** Boiling water is an effective method to kill *E. histolytica* cysts but may not be practical or feasible for large-scale water treatment due to energy requirements and logistics. However, it is not mentioned as an option here.
- **Option B:** This option is not provided, but typically, filtration could be considered if it involves specific filters designed to remove cysts (e.g., filters with pores of 1 micron or smaller). However, standard filtration methods might not be 100% effective against amoebic cysts without additional treatment steps.
- **Option C:** This option is also not provided but could involve chemical treatments other than chlorination. While there are other disinfectants, chlorination is preferred for its effectiveness, ease of application, and residual effect that helps prevent re-contamination.

## Clinical Pearl / High-Yield Fact
A key point to remember is that *E. histolytica* cysts are highly resistant to chlorination compared to bacteria and viruses, requiring a higher dose or longer contact time for inactivation. For practical purposes, ensuring that water treatment facilities use adequate chlorination protocols is crucial for preventing amoebiasis outbreaks.

## Correct Answer Line
**Correct Answer: D. Chlorination.**