Introduction:
Tap water can sometimes contain germs or microorganisms that can cause illnesses if consumed. Therefore, it is important to take measures to kill or remove these germs before drinking tap water. Among the given options, boiling the tap water is the most effective method to kill germs.

Explanation:

Filtration:
- Filtration is a process that removes impurities from water by passing it through a filter.
- While filtration can remove some larger particles and sediments, it may not be effective in removing microorganisms or germs.
- Therefore, filtration alone may not be sufficient to kill all the germs present in tap water.

Condensation:
- Condensation is the process of converting water vapor into liquid water by cooling it.
- While condensation can remove impurities and contaminants from water, it may not be effective in killing germs.
- Germs can still survive in the liquid water formed through condensation.

Decantation:
- Decantation is the process of separating liquids from solids by pouring off the liquid without disturbing the sediment.
- Decantation is not a suitable method for killing germs in tap water.
- It only helps in separating larger particles or sediments from the water, but microorganisms may still be present.

Boiling:
- Boiling tap water is the most effective method to kill germs present in the water.
- When water is boiled, it reaches a temperature of 100 degrees Celsius (212 degrees Fahrenheit), which is sufficient to kill most types of microorganisms, including bacteria, viruses, and parasites.
- Boiling tap water for at least one minute can ensure that the water is safe to drink by killing all harmful germs.

Conclusion:
Among the given options, boiling tap water is the most effective method to kill germs. Filtration, condensation, and decantation may remove some impurities or sediments from the water, but they may not be effective in killing microorganisms. Boiling tap water for at least one minute can ensure the water is safe to drink by killing all harmful germs.