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)was/at is correct as laughed indicates the use of simple past tense and at indicates a specific matter. The other options are wrong as with, were, and is indicate inclusion, plural noun, and present tense respectively. These uses don't fit in the given question. The correct answer is B)was/at.