The singular possessive form is Karen Jones's; for example:
This is Karen Jones's sister.
karen's
The possessive form is Amos's.
The singular possessive form is herd's.
The singular possessive form is heart's; the plural possessive form is hearts'.
The singular possessive form is lesson's.
The singular possessive form is grotto's.
Jones's
Jones's
The singular possessive form is week's.
The singular possessive form of "classmate" is "classmate's."
The possessive form is Amos's.
The singular possessive form of "gypsy" is "gypsy's."
The singular possessive form of "countries" is "country's".
The singular form is goose; the singular possessive form is goose's.The plural form is geese; the plural possessive form is geese's.
The singular possessive form of county is county's.
Quantum is singular, not singular possessive. The singular possessive form is quantum's.
singular possessive: boy'splural possessive: boys'
The singular possessive form is frontiersman's.