The correct option to complete the sentence "Invariably, he ends his letters .... amicably" is D. yours. Let's break down why this is the correct choice and why the other options are incorrect. Explanation of the Correct Answer (D. yours)

1. Understanding the Context: The sentence is about how someone concludes their letters. The word "amicably" suggests a friendly or pleasant tone, which is often reflected in the way one signs off a letter.
2. Correct Form: The phrase "yours" is a common and appropriate way to sign off a letter. It is a possessive pronoun that indicates that the writer is expressing a friendly sentiment towards the recipient. The full phrase might be something like "Yours sincerely" or "Yours truly," which are standard ways to end a letter.
3. Grammatical Structure: In English, when signing off a letter, we typically use "yours" followed by a comma. It is a standalone expression that conveys a sense of belonging or connection to the recipient.

Why the Other Options Are Incorrect

• A. you: This option is incorrect because "you" is a pronoun that refers to the person being addressed. It does not fit the context of signing off a letter. The phrase would be incomplete and nonsensical in this context.
• B. your's: This option is also incorrect. The term "your's" is a common misspelling of "yours." In English, "yours" is the correct possessive form, while "your's" does not exist in standard English usage. Therefore, this option is not suitable.
• C. yours': This option is incorrect because "yours'" suggests a possessive form that is not needed here. The apostrophe indicates possession, but "yours" is already a possessive pronoun that does not require an apostrophe. Thus, "yours'" is grammatically incorrect.

Summary of Key Points

• The correct answer is D. yours, which is a standard and friendly way to sign off a letter.
• "You" (A) does not fit the context of a letter closing.
• "Your's" (B) is a misspelling and not a valid form in English.
• "Yours'" (C) is grammatically incorrect due to the unnecessary apostrophe.

Revision Summary

• The correct option to complete the sentence is D. yours.
• "Yours" is a standard way to sign off letters, indicating a friendly tone.
• Options A, B, and C are incorrect due to grammatical errors or inappropriate context.
• Always ensure to use the correct possessive forms in writing to maintain clarity and correctness.