Select the sentence with proper punctuation in a possessive form: 

1. The childrens toys were scattered
2. The childrens’ toys were scattered
3. The children’s toys were scattered,
4. The childrens’s toys were scattered

Plural nouns not ending in s take ‘s (Merriam-Webster). “Children” is already plural (irregular), so adding just an apostrophe (option b) is incorrect. Regular plurals (e.g., “dogs’ toys”) use only an apostrophe. Option d doubles the possessive marker unnecessarily.