Step 1: Understanding the Concept:
This question tests the correct use of determiners and quantifiers with a singular countable noun ('chair').
Step 2: Detailed Explanation:
- (A) More: "More chair is required" is incorrect. 'More' is typically used with plural nouns ("more chairs") or uncountable nouns ("more furniture"). To use it with a singular noun, you would need another determiner, e.g., "One more chair is required."
- (B) Much: Incorrect. 'Much' is used with uncountable nouns (e.g., much water, much time). 'Chair' is a countable noun.
- (C) Many: Incorrect. 'Many' is used with plural countable nouns (e.g., many chairs).
- (D) An extra: "An extra chair is required." This is grammatically correct. 'An extra' means 'one more' or 'an additional' chair. It functions as a determiner for the singular noun 'chair'.
Step 3: Final Answer:
The correct option is (D) because "An extra" is the only option that correctly modifies the singular countable noun "chair".