In this spelling based English question, four options are given. Select the correctly spelt form of the word that refers to the gradual passing of a liquid through a filter or porous surface.

Introduction / Context:
This question checks your ability to recognise correct English spelling. The word being tested refers to the process in which a liquid slowly passes through a filter or porous surface, such as water passing through soil. This word is often used in science and engineering contexts and appears in academic reading passages as well as technical descriptions.

Given Data / Assumptions:

- Intended word: the process where a liquid gradually filters through a medium. - Options: percoletion, parcolation, percolation, parcoletion, percolasion. - Only one matches standard dictionary spelling.

Concept / Approach:
The correct spelling of the word is "percolation", with the letters P E R C O L A T I O N. It comes from the verb "percolate", which means to filter gradually through a porous surface. The main challenge in such questions is distinguishing between similar looking vowels and consonants. You should use your memory of reading scientific or geographical texts, where "percolation of water" is a common phrase, to guide you to the correct choice.

Step-by-Step Solution:

Verification / Alternative check:
Insert the options into a familiar expression. "The percolation of rainwater through soil" is a standard phrase in geography and environmental science. If you try "percoletion of rainwater" or "percolasion of rainwater", they look and sound wrong. You can also think of similar noun forms like "circulation", "migration", and "vibration", all of which end with "-ation" rather than "-letion" or "-asion". This pattern supports "percolation" as the correct form.

Why Other Options Are Wrong:
"Percoletion" and "parcoletion" misuse the ending "-letion", which does not match the spelling of the related verb "percolate". "Parcolation" and "parcoletion" misspell the first syllable "per" as "par", changing the root completely. "Percolasion" uses "-sion" instead of the usual "-tion" suffix for forming nouns from verbs like percolate. Since spelling in English is largely fixed for standard academic words, all of these variations are considered incorrect.

Common Pitfalls:
Students often rely on how a word sounds, which can be misleading, especially for endings like "-tion" and "-sion". Another problem is mixing up similar words like "circulation" and "correlation", which can lead to confusion in the middle consonants. The best strategy is to connect noun forms back to their base verbs and remember the standard transformation, such as "percolate" becoming "percolation". Over time, exposure to correct spelling in textbooks and articles makes such questions easier.

Final Answer:
The correctly spelt word is "percolation", so the correct answer is Percolation.