Understanding Sentence Structure and Grammar

The question asks to identify the grammatically correct sentence among the given options. This involves understanding subject-verb agreement and the correct usage of determiners like 'Every', 'Each', 'Many', and 'Any'.

Analyzing Each Option for Grammatical Correctness

• Option 1: Every man knows his duty.

  'Every man' acts as a singular subject. In English, singular subjects require a singular verb. The verb 'knows' is the third-person singular present tense form of 'know'. The possessive pronoun 'his' agrees with the singular subject 'man'. This sentence follows the rules of subject-verb agreement and is grammatically correct.

• Option 2: Each man knows his duty.

  Similar to 'Every man', 'Each man' also acts as a singular subject and requires a singular verb. The verb 'knows' is singular, and 'his' is the correct possessive pronoun. This sentence is also grammatically correct.

• Option 3: Many man knows his duty.

  'Many' is used with plural countable nouns. The correct form would be 'Many men'. With the plural subject 'men', the verb should be plural ('know'). The possessive pronoun would also be plural ('their'). Therefore, 'Many man knows his duty' is grammatically incorrect due to the singular noun 'man' used with 'Many' and the singular verb 'knows' used with what should be a plural subject.

• Option 4: Any man knows his duty.

  'Any' is typically used in negative sentences, questions, or conditional clauses. In a positive declarative sentence like this, while 'Any man' is treated as singular (taking 'knows'), the usage is less common and often sounds awkward compared to 'Every' or 'Each' when referring to all members of a group generally. The sentence structure is grammatically possible but less natural or common in this context.

Conclusion

Based on standard English grammar rules, both Option 1 ("Every man knows his duty.") and Option 2 ("Each man knows his duty.") are grammatically correct sentences. However, in multiple-choice questions, one option is typically intended as the best or correct answer. Focusing on the structure and common usage, 'Every man knows his duty' is a widely accepted and grammatically sound sentence.

Therefore, the correct option is the one that presents a grammatically sound sentence.