You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For consistency, answers should be in all lower cased letters.

Category: THE FOURTH WORD 
Clue: In Mark Antony's eulogy for Julius Caesar in Shakespeare, after the crowd quiets down
lend

Category: SEX CHANGES 
Clue: Don't let the pearls fool you, these lady bivalves can change into males when it suits them
oysters

Category: "Y"? 
Clue: From the Middle English for "to boast", it's a short, sharp cry from a dog in pain

a yelp