The plural of buyer is buyers.
As in "the buyers have arrived".
The possessive form of the plural noun buyers is buyers'.
example: We have the presentation ready for the buyers' meeting.
Purchase.
purchasers'
Quantum is singular, not singular possessive. The singular possessive form is quantum's.
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 pronouns are "my," "mine," "your," "yours," "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 form of "test" is "test's".
Buzz's is the singular possessive.
The singular possessive is biker's; the plural possessive is bikers'.
The singular possessive of criteria is criteria's.