Answer: The sentence that shows correct capitalization is the second one: "My uncle once met the Queen of England".
Step-by-step explanation: According to the capitalization rules, the first letter of words that make reference to a family relationship, such as "uncle" or "aunt", should not be capitalized unless these words are followed by the proper name of that person. In the sentence provided, the word "uncle", which is a common noun, is not followed by a proper name (for example, "Bob" or "James"); therefore, the "u" should not be capitalized. Moreover, the "q" and the "e" in "Queen" and "England" should be in capital letters because the initial letter of royal titles and countries need to be capitalized. In that way, the sentence that shows correct capitalization is "My uncle once met the Queen of England".