The B&O Railroad's tracks ran throughout the small town. (one railroad with singular possessive)The railroads' officers were keen to expand rail service in the 1800s. (more than 1 railroad, and plural possessive. This also means that "officers" indicates groups of men, one group per railroad company, but here used as a generic plural, no possessive.)The railroad's conductor got married. (One specific railroad as singular possessive for one specific conductor.)The railroads' conductors were mostly single men. (plural possessive, plural railroad companies with plural conductors).
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 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 form of "classmate" is "classmate's."
Taco's is the singular possessive.
The singular possessive of dish is dish's
The singular possessive is Martin's.
Buzz's is the singular possessive.
The singular possessive is fish's.
Grave's is the singular possessive.