The sentence in option (b) has an error. In the sentence, the use of the preposition 'on' is incorrect as it means 'physically in contact with and supported by (a surface)' and instead the preposition 'in' (as an integral part of a larger group) is the appropriate preposition that should be used in the sentence.
Hence, the correct answer is option (b).
Note:
A Preposition is a word placed before a noun or a pronoun or a noun equivalent (pronoun, adverb, gerund, infinitive, adverbial clause, or any clause that can be used as the object of the preposition) and shows a relationship in space or time or a logical relationship between two or more people, places, or things in a sentence.
Examples
I. The teacher scolded the child for being late.
II. We're going to a party.
· The words in bold are called prepositions because they normally take position before (pre) a noun/pronoun or a noun equivalent (pronoun, adverb, gerund, infinitive, adverbial clause, or any clause that can be used as the object of the preposition.
· The noun/pronoun which is used with a preposition is called its Object.