<improved answer>
The singular possessive form of monkey is monkey's.
For a singular possession to be shown, you would formulate the sentence to show that the monkey has something (possession) or owns something (possession) by adding an apostrophe after monkey.
Example: The monkey's hair was blonde.
Singular: hypothesis Plural: hypotheses
pilot's
Actress'
Radios' is the plural possessive of the singular noun radio.
Plural possesive.
The singular possessive form of city is city's
The singular form of the plural noun smiths is smith.The singular possessive form is smith's.example: I bought this at a goldsmith's shop on Main Street.
The singular possessive form of "tooth" is "tooth's."
Singular: hypothesis Plural: hypotheses
pilot's
Actress'
enemy's
The possessive form of the singular noun monkey is monkey's.example: The monkey's tail was wrapped around a branch.
The singular possessive noun for child is child's.
Buses' is plural possesive.
Dad? Although father is already singular "My father's car" singular possesive
his