Fill in the blanks with the appropriate article. _______ moon looks beautiful.

Explanation:

Answer: the

Use the definite article 'the' when referring to something specific or unique that is known to both the speaker and the listener. Earth's Moon is a single, identifiable object, so we say 'the moon'.

• Correct usage example: The moon looks beautiful.

• Why 'a' is wrong: 'a' is used for a nonspecific singular noun (for example, 'a star'), not for a unique, known object like the Moon.

• Why 'an' is wrong: 'an' is used before words that begin with a vowel sound (for example, 'an hour'); 'moon' begins with a consonant sound.

• Why no article is wrong: Singular countable nouns generally need an article or determiner. Omitting the article is only correct for certain plural or uncountable nouns when speaking generally.

Therefore, the correct choice is the.