Fill in the blank with an appropriate 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)by is correct as it is used to show the thing or person that does something. The other options are wrong as with, of, and for indicate inclusion, possession, and a purpose respectively. These uses don't fit in the given question. The correct answer is B)by.