An ice cream vendor screams 'Ice Cream' but nobody buys-him.

With: This preposition suggests the vendor is offering something alongside the ice cream, which isn't implied in the sentence. At: This preposition implies aiming or directing the screams, but the sentence focuses on the lack of sales, not the direction of the vendor's action. Off: This isn't grammatically correct in this context. Of: This preposition indicates possession or derivation. In this case, it implies that the "lack of buying" is something the vendor experiences "by virtue of" his profession or role as an ice cream seller.