The form churches is the plural of the noun "church."
example: There are three churches on this street.
The form church's is the singular possessive noun.
example: There was a special request for donations to repair the church's roof.
The plural form of the noun church is churches.
It is church.
churchs
Muslims call their churches "Mosques"
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
The singular possessive is Martin's.
The singular possessive is fish's.
Grave's is the singular possessive.
The singular possessive is test's.
Buzz's is the singular possessive.
The singular possessive is biker's; the plural possessive is bikers'.