Choose the option that fills the blank with the most suitable word:
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 indicates an agent. The other options are wrong as from, with, and in indicate a source, inclusion, and the inside of a place respectively. These uses don't fit in the given question. The correct answer is B)by.