Fill in the blank with the most appropriate 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 A)during is correct as it indicates a duration. The other options are wrong as for, since, and at indicate a purpose, a duration with a given starting point, and a specific location respectively. These uses don't fit in the given question. The correct answer is A)during.