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 C)since is correct as it indicates a duration which has its starting point of time given. The other options are wrong as on, from, and for indicate a surface, a source, and a purpose respectively. These uses don't fit in the given question. The correct answer is C)since.