'None of us knew the way.'
The correct tag question corresponding to the sentence above is:

The correct answer is Option A (Did we?).

Key Points:
• Core Concept: Question tags are short questions added at the end of statements. The polarity rule states that a negative statement requires a positive question tag, while an affirmative statement requires a negative tag.
• Correct Option Analysis: Option 1 ('Did we?') is correct. The subject of the main clause is 'None of us'. The word 'None' is inherently negative in meaning, making the statement negative overall. Consequently, the tag must be positive. Since 'knew' is in the simple past tense, the auxiliary verb used for the tag is 'did'. The pronoun corresponding to 'us' in 'None of us' is 'we'. Therefore, the correct tag is 'Did we?'.
• Incorrect Options Analysis:
• Option 2 ('Didn't we?'): Incorrect because using a negative tag ('didn't') with a statement that contains a negative word ('None') creates a double negative, violating the positive tag rule for negative statements.
• Option 3 ('Did none ?'): Incorrect because 'none' is a pronoun used in the main clause, not a personal subject pronoun suitable for a question tag (such as I, we, you, he, she, it, they).
• Option 4 ('Didn't none ?'): Incorrect due to both improper pronoun usage and incorrect negative polarity.
• Exam Trap: Candidates often miss negative words like 'none', 'hardly', 'barely', 'scarcely', 'neither', or 'seldom' and mistakenly assume the sentence is positive because it lacks 'not'. Always treat statements with these words as negative and select a positive tag.
• Key Takeaway: Remember: Words like 'none', 'hardly', and 'few' make a statement negative, so the question tag must always be positive.