I do not know if this is a multiple choice question or not, but I would argue that the answer is "jest," since this dialogue, and the scene it belongs to, are very comical. Mercutio and Romeo, who has just arrived, are joking with each other. Romeo challenges his friend to keep going, since he thinks that Mercutio is better at telling jokes ("[...] wast not here for the goose"), and Mercutio replies by saying that he will bite Romeo's ear, as if he was a goose, and when Romeo begs him not to bite him, Mercutio compares Romeo's jokes and humor with bitter and spicy flavors. Therefore, the word "jest" illustrates for and helps the reader understand the comical and hilarious mood of the passage.