Class is singular (even though it ends in an -s). One class, in the possessive, is class's. "The class's group project is due next Monday." But if it's more than one class, you have classes. And classes' is the plural possessive form.
The word sisters' is plural possessive. The singular is sister, singular possessive is sister's; the plural is sisters, the plural possessive is sisters'.
The singular possessive form is heart's; the plural possessive form is hearts'.
The singular possessive is author's. The plural possessive is authors'.
Both the singular and plural form is corps; the singular or plural possessive is corps'.
Tess = singular Tess's = singular possessive Tesses = plural Tesses's plural possessive
Museum is singular. Museum's is singular possessive. Museums is plural. Museums' is plural possessive.
The singular possessive of "ant" is "ant's" and the plural possessive is "ants'".
Singular possessive: secretary's Plural: secretaries Plural possessive: secretaries'
The singular possessive is biker's; the plural possessive is bikers'.
The word sisters' is plural possessive. The singular is sister, singular possessive is sister's; the plural is sisters, the plural possessive is sisters'.
The singular possessive is army's.The plural possessive is armies'.
The singular possessive is avocado's; the plural possessive is avocados'.
Singular possessive: mother's Plural possessive: mothers'
Niece's is a singular possessive noun. niece - singular nieces - plural niece's - singular possessive nieces' - plural possessive
Women's is a plural possessive. The singular possessive is woman's
The singular possessive form is heart's; the plural possessive form is hearts'.
The singular possessive form is headdress's. The plural possessive form is headdresses'.