In the following question, four English words are given, out of which one word is incorrectly spelt. Carefully identify and select the incorrectly spelt word.

Introduction / Context:
Spelling questions in competitive English exams often test whether you can distinguish between correctly and incorrectly spelt words that look very similar. In this item, you are asked to focus on four words, three of which are spelt correctly and one of which is spelt wrongly. Your job is to spot the incorrect spelling by using your vocabulary knowledge and visual memory of standard English spellings.

Given Data / Assumptions:
- The question clearly asks for the incorrectly spelt word, not the correct one.
- The options given are: impecunous, Impudence, Incongruous, Indomitable, and Impetuous (additional option).
- We assume standard British or international English spellings that appear in reputable dictionaries and textbooks.

Concept / Approach:
The key to solving such questions is to recall the standard spelling of each word and compare it to the option presented. The intended word behind “impecunous” is “impecunious”, which means someone who is poor or lacking money. The other words – “impudence”, “incongruous”, “indomitable” and “impetuous” – are all correctly spelt. Therefore, the incorrectly spelt word is the one missing the letters “io” in the middle: “impecunous”.

Step-by-Step Solution:
Step 1: Recognise that “impecunous” is probably meant to represent the word “impecunious”.
Step 2: Recall or check mentally that the correct spelling is i-m-p-e-c-u-n-i-o-u-s, containing the “io” sequence before the final “us”.
Step 3: Examine “Impudence”: it correctly represents the noun from “impudent”, meaning rudeness or disrespect.
Step 4: Note that “Incongruous” (not in harmony) and “Indomitable” (impossible to defeat) are also standard dictionary spellings, as is “Impetuous” (acting hastily).
Step 5: Conclude that “impecunous” is the only option that does not match its well-known correct form.

Verification / Alternative check:
If you have encountered the phrase “impecunious student” or “impecunious artist” in reading passages, you will remember the sequence “-nious” at the end. Words like “harmonious”, “ingenious” and “continuous” also carry similar endings. This pattern reinforces that “impecunous” is incomplete. Meanwhile, searching your memory for alternative spellings of “impudence”, “incongruous”, “indomitable” and “impetuous” will not yield any commonly accepted variant, confirming that they are correctly spelt.

Why Other Options Are Wrong:
- “Impudence”: correct noun form of “impudent”; no extra or missing letters.
- “Incongruous”: standard spelling describing something that does not fit its surroundings or context.
- “Indomitable”: correctly expresses the idea of being unconquerable or determined.
- “Impetuous”: accurately spelt word for acting without thought; there is no common alternative spelling like “impetous”.

Common Pitfalls:
Students sometimes assume that the least familiar word must be wrong, but difficulty is not the same as incorrect spelling. The right approach is to think of the known correct form of each word. In this question, “impecunious” is a common exam word and is frequently tested, so if you have revised vocabulary lists you will quickly see that “impecunous” is missing “io”. Train yourself to focus on vowel clusters and common suffixes such as “-ious”, “-eous” and “-uous” in advanced adjectives.

Final Answer:
The incorrectly spelt word is “impecunous”.