In the following question, a word has been written in four different ways, out of which only one is correctly spelt. Select the correctly spelt word.

Introduction / Context:
This spelling question asks you to identify the standard English spelling of a common noun related to interest and desire to know. Such questions test visual memory of words that you have seen in reading and writing. Even small vowel changes or letter insertions can make a word incorrect in competitive exams.

Given Data / Assumptions:

• The target word is the noun meaning “a strong desire to know or learn something”.
• Options: Curosity, Curoucity, Curiosity, Cuoisity.
• We must choose the spelling that matches dictionary and standard usage.
• The base adjective is curious, from which the noun is formed.

Concept / Approach:
The adjective curious is spelt c u r i o u s. The noun is formed by replacing the ous ending with osity, giving curiosity: c u r i o s i t y. None of the distractors follow this pattern correctly. In exam spelling questions, it is helpful to recall the base form and how common suffixes like ity or osity are added.

Step-by-Step Solution:
Start from curious: c u r i o u s.Replace ous with osity to form the noun: c u r i o s i t y.This gives curiosity as the correct spelling.Check each option visually:Curosity – letters r and i are misplaced; it should be curi-, not curo-.Curoucity – extra letters o and u and an incorrect c i t y ending; not standard.Cuoisity – incorrect ordering of u and r and wrong vowel sequence.Curiosity matches the known base + suffix pattern and is the only standard form.

Verification / Alternative check:
Think of common phrases: “out of curiosity”, “childhood curiosity”, “intellectual curiosity”. In books, newspapers and exams, you always see curiosity spelt as c u r i o s i t y. None of the other options appears in normal printed English. If you imagine writing the word while pronouncing it slowly (kyoo-ree-oss-ih-tee), curiosity fits the sound pattern more naturally than the other distorted forms.

Why Other Options Are Wrong:
Curosity drops the i after r and thus does not follow the correct root curious. Curoucity inserts extra vowels and adds the city ending, which is a different word entirely. Cuoisity scrambles the order of vowels and consonants, making it unnatural and inconsistent with the adjective curious. Exam rules are strict: even a single misplaced letter renders a spelling wrong, so all three of these must be rejected.

Common Pitfalls:
Because curiosity is a very common word in speech but slightly less carefully observed in writing, learners may have a vague memory of the sound but not the exact letter sequence. A helpful strategy is to anchor the spelling to the base adjective: curious → curiosity by swapping ous for osity. Recognising this pattern not only confirms the spelling of curiosity but also helps you with related pairs in English where adjectives ending in ous form nouns ending in osity.

Final Answer:
The correctly spelt word is Curiosity.