In the following question, four words are given, out of which one word is incorrectly spelt. Identify the incorrectly spelt word that does not match standard English spelling.

Introduction / Context:
This spelling question checks familiarity with common but slightly advanced English words. Competitive examinations deliberately include such items to ensure that candidates can distinguish correct spellings from near correct lookalikes. Here, three options are correctly spelt words, while one option has a missing letter. Identifying the incorrect spelling helps improve accuracy in written communication and in reading comprehension, where such words often appear in editorials and essays.

Given Data / Assumptions:

• Four options are given: “Pertinacious”, “Demarcation”, “Temperament”, and “Sureptitious”.
• We must find the one word that is incorrectly spelt according to standard English.
• We assume modern standard spelling used in reputable dictionaries and textbooks.

Concept / Approach:
The key to this question lies in knowing or recognising the word “surreptitious”, which means secret or done by stealth. The correct spelling has a double “r” and a double “t” in the middle: s u r r e p t i t i o u s. In the option list, the word appears as “Sureptitious”, missing one “r” and having an incorrect sequence of letters. The other three words are correctly spelt: “Pertinacious” means stubbornly persistent, “Demarcation” means marking a boundary, and “Temperament” refers to a person’s natural disposition. Since only “Sureptitious” fails to match a correct English word, it is the incorrectly spelt option.

Step-by-Step Solution:

Verification / Alternative check:
We can verify by using each word in a sample sentence. For instance, “Her pertinacious questioning finally revealed the truth” uses “pertinacious” correctly. “There is a clear demarcation between the two plots of land” shows “demarcation” in a natural context. “His calm temperament makes him a good leader” is also standard. In contrast, if we try “He made a sureptitious phone call during the meeting”, we realise that common dictionaries and style guides use “surreptitious” in this place. This mismatch confirms that “Sureptitious” is wrong. Spell checking tools and official word lists also recognise “surreptitious” but not “sureptitious”.

Why Other Options Are Wrong (they are correct spellings):

• Option A: “Pertinacious” is correctly spelt and means very persistent or stubborn in holding an opinion or course of action.
• Option B: “Demarcation” is correctly spelt and refers to a boundary or clear separation between areas, ideas, or groups.
• Option C: “Temperament” is correctly spelt and denotes a person natural character or typical mood pattern.

Common Pitfalls:
Spelling questions often include words that are less familiar to test whether candidates truly know them rather than simply recognising them vaguely. Learners may be tempted to mark a word as wrong just because they have not seen it before. Another pitfall is ignoring internal double consonants, such as the double “r” and “t” in “surreptitious”. To overcome this, it is helpful to read widely and pay attention to commonly tested words in practice sets. Grouping words by roots and similar patterns also helps, for example remembering that “surreptitious”, “suspicious”, and “fictitious” share the “itious” ending.

Final Answer:
The incorrectly spelt word is “Sureptitious”, which should be correctly written as “surreptitious”.