Four spellings of the same word are given. Out of these, choose the correctly spelt word.

Introduction / Context:
This question tests spelling recognition for a word frequently used in formal writing and exam explanations. The word means containing an error or incorrect. Accurately spelling such words is important for clear written communication. The exam provides four variations, three of which contain common types of mistakes, such as missing letters or misplaced vowels, and one of which is the correct spelling used in standard English.

Given Data / Assumptions:

• Options: Erroneous, Eronneous, Erronous, Eroneous.
• The task is to select the correctly spelt word.
• We assume standard British or international spelling conventions.
• All options aim to represent the adjective meaning wrong or incorrect.

Concept / Approach:
The correct spelling of the word is Erroneous, with the pattern e r r o n e o u s. This word is derived from error and keeps the double r and the sequence e o u s at the end. The incorrect options either drop one of the r letters, misplace vowels, or both. Recognising the root error and the typical adjective ending eous helps identify the correct form quickly.

Step-by-Step Solution:
Step 1: Recall that the root is error, spelt e r r o r, and the adjective form is formed by changing the ending to e o u s, giving erroneous. Step 2: Examine option A, Erroneous. It contains double r after the initial e and the ending e o u s, giving e r r o n e o u s, which is the standard spelling. Step 3: Examine option B, Eronneous, which has only one r at the beginning and double n in the middle, deviating from the root error. Step 4: Examine option C, Erronous, which keeps double r but omits the e before o u s at the end, so the ending is o n o u s instead of o n e o u s. Step 5: Examine option D, Eroneous, which uses only one r and disrupts the clear connection to error. Step 6: Conclude that Erroneous is the only option that matches the correct and commonly accepted spelling.

Verification / Alternative check:
In usage, one often reads phrases like erroneous judgment or erroneous assumption. Replacing erroneous with any of the other options would be instantly marked wrong by a spell checker or editor. The pattern of forming adjectives with eous is also found in words like spontaneous and courageous, which helps reinforce the correctness of the e o u s ending. Checking a reliable dictionary confirms that Erroneous is the only valid spelling among the given choices.

Why Other Options Are Wrong:
Eronneous is wrong because it changes the double r at the start to a single r and introduces an unnecessary double n, breaking the link with error. Erronous is wrong because it drops the e before the o u s ending, resulting in an unusual letter combination not recognised as standard. Eroneous is wrong because it again uses a single r and distorts the derivation from error. None of these forms appears in formal texts or dictionaries as correct English words.

Common Pitfalls:
Learners frequently delete or misplace vowels when encountering longer adjectives, especially those ending with eous or ious. They may also forget which consonant is doubled in the root. A practical strategy is to remember base words and examine how standard suffixes are added. In this case, knowing error plus eous leads directly to erroneous, and any version that breaks this pattern can be safely rejected in a multiple choice setting.

Final Answer:
The correctly spelt word is Erroneous.