In the following question, four spellings of the same word are given. Select the correctly spelt form of the verb meaning to make a person or animal protected against a disease.

Introduction / Context:
Spelling accuracy is an important aspect of written communication, especially for scientific or medical terms that are often used in exams and professional contexts. This question focuses on the correct spelling of the verb meaning to make a person or animal resistant to a disease by giving a vaccine. The standard English spelling of this verb is immunize, and the distractor options present common errors in vowel quantity and sequence.

Given Data / Assumptions:

• Four variants are given: imunize, immunaize, imunaize, immunize.
• Only one is an accepted dictionary spelling in standard English.
• The word refers to the process of making someone immune through vaccination.
• We follow general international usage where immunize is the usual spelling.

Concept / Approach:
The correct spelling of the verb comes from the base word immune combined with the suffix ize. The word immune itself has two m letters: i m m u n e. When the suffix ize is added, the spelling becomes immunize with the double m preserved. The vowel sequence u n i remains intact. Any option that either drops one m or adds extra vowels that do not belong is incorrect. Recognizing the root word immune makes it easier to verify the spelling.

Step-by-Step Solution:
Step 1: Recall the base word immune and note that it contains double m. Step 2: Understand that the verb form is created by adding the suffix ize to immune, resulting in immunize. Step 3: Examine option A, imunize, which contains only one m and therefore loses the link to the base word immune. Step 4: Examine option B, immunaize, which inserts an unnecessary a after n and does not reflect the standard pattern of suffixation. Step 5: Examine option C, imunaize, which both uses a single m and adds the extra ai vowel combination, creating multiple deviations from the correct form. Step 6: Examine option D, immunize, which preserves the double m and follows the logical pattern immune plus ize. Step 7: Conclude that immunize is the correctly spelt verb.

Verification / Alternative check:
The spelling immunize is widely used in medical literature, vaccination campaigns, and health policy documents. When checked against reliable dictionaries, immunize always appears as the correct form, sometimes accompanied by the British variant immunise with s instead of z. None of the distractor options match any recognized standard variant. Thus, comparing with the base word immune and with dictionary usage confirms immunize as the correct choice.

Why Other Options Are Wrong:
Imunize drops one m and does not reflect the double m that is an essential part of the root, making it a typical under spelling error. Immunaize is incorrect because of the extra vowel a, which distorts the word structure and does not match any accepted spelling. Imunaize combines both errors by using a single m and inserting ai, creating a word that is far from the original. None of these appear as valid entries in standard references.

Common Pitfalls:
Learners often mis spell words with double consonants and confusing vowel sounds, particularly in the field of medicine where many words are derived from Latin or French. They may overgeneralize patterns from other words ending in ize that do not contain a double consonant. To avoid such errors, it is helpful to remember the root immune and then simply attach ize, keeping the original consonants unchanged. Repeated exposure to correct spelling in context also strengthens memory.

Final Answer:
The correctly spelt word is immunize.