Singular possessive form of jars is jar's.
example: The jar's lid required some real muscle.
Quantum is singular, not singular possessive. The singular possessive form is quantum's.
Museum is singular. Museum's is singular possessive. Museums is plural. Museums' is plural possessive.
The singular possessive pronouns are mine, yours, his, hers, and its. The singular possessive adjectives are my, your, his, her, and its.
The singular possessive of dish is dish's
Grave's is the singular possessive.
The singular possessive is test's.
The singular possessive is Martin's.
The singular possessive is fish'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.
There's no such thing as a singular possessive verb. Chris's is a singular possessive noun.