There are two accepted forms for possessive singular nouns ending in s:
Add an apostrophe (') after the existing s at the end of the word: Julius'
Add an apostrophe s ('s) after the existing s at the end of the word: Julius's
Examples:
Aunt Hazel is having a party for Uncle Julius' birthday.
Aunt Hazel is having a party for Uncle Julius's birthday.
Note: The -s's is the most commonly used form, but if you are a student, use the form that is preferred by your teacher.
The singular possessive of Julius is "Julius's" or "Julius'".
Julius'
The singular possessive form of "test" is "test's".
The singular possessive pronouns are "my," "mine," "your," "yours," "his," "her," and "its."
The singular possessive form of "classmate" is "classmate's."
Taco's is the singular possessive.
The singular possessive form of county is county's.
Quantum is singular, not singular possessive. The singular possessive form is quantum's.
The singular possessive of "ant" is "ant's" and the plural possessive is "ants'".
Museum is singular. Museum's is singular possessive. Museums is plural. Museums' is plural possessive.
The singular possessive pronouns are "my," "mine," "your," "yours," "his," "her," and "its."
The singular possessive of dish is dish's
The singular possessive is Martin's.
The singular possessive is fish's.
Grave's is the singular possessive.
The singular possessive form of "test" is "test's".
Buzz's is the singular possessive.
The singular possessive is biker's; the plural possessive is bikers'.
The singular possessive of criteria is criteria's.