Answer: children's
Step-by-step explanation: A noun names a person, place, thing, idea, quality or action. A possessive noun shows ownership by adding an apostrophe, an "s" or both. To make a single noun possessive, simply add an apostrophe and an "s." This also applies to plural nouns that do not end with an "s" for example the possessive form of "children" is "children's." If the noun is plural and ends with an "s" we should only put an apostrophe at the end of the word.