Fill in the blanks with the most appropriate words.
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)when/on/of is correct as on and of indicate a specific day and a specific month respectively. The other options are wrong as in, indicates inside something and what indicates something that is irrelevant. These uses don't fit in the given question. The correct answer is B)when/on/of.