Which sentence contains an incorrect possessive form?
a. We borrowed Ashley's large wooden spoon.
b. The boys joke made us all laugh.
c. I followed Grandmother's pasta recipe.
d. Dirty bowls covered the kitchen counter.
The sentence that contains an incorrect possessive form is B) The boys joke made us all laugh. If it's possessive, it the joke belongs to them, is told by them, it should go like this: The boys' joke made us all laugh.