Singular possessives of nouns always use the apostrophe S regardless of their spelling.The possessive would be genius's (e.g. a genius's IQ is very high).
The above sentence should read: Benjamin Franklin was one of America's greatest citizens.America's is the possessive.
Yesterday is a noun in that sentence.
Yesterday was the day before today.
"That's yesterday's news..." uses 'yesterday' to qualify the pronoun 'news'.
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.
The singular possessive is biker's; the plural possessive is bikers'.