"The correct answer is option 4) i.e. Irrelevant. Explanation    The word 'Pertinent' means having a clear decisive relevance to the matter in hand. The synonyms of the word are applicable, apposite, apropos, germane, material, pointed, relative, relevant. The antonyms of the word are irrelevant,​ extraneous, immaterial, impertinent, inapplicable, inapposite, irrelative, pointless. From the antonym of the given word 'Pertinent', we can say that the word 'Irrelevant' is its opposite meaning. The word 'Irrelevant' means not having anything to do with the matter at hand. Hence, we can say that 'Irrelevant' is nearly opposite in meaning to the given word. Let's see the meaning of other given options- WORDS MEANING Irrational not governed by or according to reason Irregular  not being or acting in accord with laws, rules, or established custom Inconsistent  lacking consistency     The word 'Pertinent' is derived from the Middle English, from Anglo-French, from Latin pertinent-, pertinens Its first known use was in the 14th century. Examples of 'Pertinent' in a sentence: They could hence offer pertinent solutions to numerous emerging applications. The reliability and the accuracy of the rate constants pertinent to these exciting species were evaluated." Answer from Testbook on testbook.com