Answer:
The line in this excerpt from Shakespeare's Romeo and Juliet that foreshadow the tragic fate of Romeo and Juliet is the third one: "Then love-devouring death do what he dare;".
Step-by-step explanation:
In this line, the reader can suspect the end of the story because death here is presented as a monster that ends with the love between Romeo and Juliet. Here, death is the figure that will end with everything on its way, the "love-devouring", the one that wins in the end and the one that comes with a tragic ending. This line announces the fate of Romeo and Juliet by giving the reader the clue of what will happen.