Identify the possessive noun in the following sentence.
The clever girl’s plan to trap the robbers worked.

• An apostrophe could be a mark that indicates the possessive type of noun. We use the possessive form to explain the nouns concerning people, groups of individuals, countries, and so.
• Possessive nouns are nouns that possess something or show the possession of something. While singular nouns become possessive with the addition of an apostrophe and ‘s’ thereto, plural nouns and words ending with ‘s’ simply need an apostrophe to that.
  Example: boy – boy’s and boys – boys’.
• In the given sentence, we identify that only girls are the term that has an apostrophe and thus indicates a genitive case. It means something that the girl possesses, in this case, her plan.
  Therefore, option B becomes the proper answer.
• Option A can not be the proper answer as ‘clever’ is an adjective and it cannot take a possessive form.
• We rule out option C as ‘trap’ is given here as a verb rather than being a noun.
  Option D is wrong as ‘robbers’ can't be the right possessive noun. 

Hence, option B is the correct answer.