Question

Is "mold's" singular or plural possessive? What about "people's"?

Answer 1

mold's singular possessive;
people's plural possessive

Explanation:

mold is a singular noun, referring to a specific culture or type of mold; when referring to a collection of different types of mold the plural form would be molds (and thus the plural possessive form would be molds'

people is the plural form of person (it is an alternate, and more common form, of persons); thus in its possessive form: people's it remains plural. (Other similar plural forms not formed by appending an "s" include: "oxen", the plural of "ox", and "geese" the plural of "goose")