Fill in the blank with a suitable preposition:
A preposition is a word which comes before a noun or a pronoun and establishes a relationship between the elements of a clause or words. Option B)in is correct as it is used to indicate an inside of a place. The other options are wrong as at, on, and from indicate a specific location, a surface, and a source respectively. These uses don't fit in the given question. The correct answer is B)in.