In the following question, a word has been written in four different ways. Choose the correctly spelt form of the word meaning “impossible to resist.”

Introduction / Context:
This spelling question asks you to select the correct form of a common English adjective meaning “impossible to resist.” Spelling questions often focus on words where similar patterns cause confusion, including endings like “able” and “ible,” or the presence of double consonants.

Given Data / Assumptions:
The four spellings given are: “Irresistable,” “Irresistible,” “Iresistible,” and “Iresistable.”
We know the word refers to something extremely attractive or tempting, often used as “irresistible offer,” “irresistible charm,” or “irresistible food.”
We assume standard modern English spelling as used in dictionaries and exams.

Concept / Approach:
The correct spelling of the word is “Irresistible,” with the pattern “ir + resist + ible.” The base verb is “resist.” The prefix “ir” is a negative marker similar to “in” and is used before words starting with “r.” The suffix that attaches is “ible,” not “able,” because in many Latin based words, “ible” is used after certain roots. The double “r” appears because the prefix “ir” ends with “r” and the base “resist” begins with “r.” Therefore, the only correct full spelling is “Irresistible.”

Step-by-Step Solution:
Step 1: Identify the base word “resist” meaning to oppose or withstand. Step 2: Add the negative prefix “ir,” which is used before words beginning with “r” to create a negative meaning, giving “irresist.” Step 3: Attach the correct adjective suffix “ible” to form “irresistible.” Step 4: Check that the word now correctly means “that cannot be resisted.” Step 5: Compare this pattern with the options and select the one that matches exactly.

Verification / Alternative check:
We can verify by recalling familiar usage: newspapers and books consistently write “irresistible temptation,” “irresistible smile,” and “irresistible force” using the “ible” ending. Dictionaries list “irresistible” with this spelling. Any form ending in “able,” such as “irresistable,” is considered incorrect. Similarly, removing one “r” as in “Iresistible” breaks the prefix pattern and is wrong.

Why Other Options Are Wrong:
“Irresistable” wrongly uses the “able” ending instead of “ible.”
“Iresistible” drops one “r,” thus losing the correct prefix “ir” plus base “resist” structure.
“Iresistable” combines both errors: it has only one “r” and the incorrect “able” ending.

Common Pitfalls:
Learners frequently confuse when to use “able” and when to use “ible” at the end of adjectives. A helpful strategy is to remember the base verb and check dictionary patterns: many words derived from Latin roots use “ible,” such as “visible,” “audible,” and “flexible.” Another pitfall is forgetting how negative prefixes change form: “in” becomes “im,” “ir,” or “il” before certain consonants. For example, “regular” becomes “irregular,” which matches the “irresistible” pattern.

Final Answer:
The correctly spelt word is Irresistible.