How were the elements of the friar's plan foreshadowed when the friar first appeared in the play? why is their timing of the friar's plan critical?

The correct answer is the following.  

The plan of Friar is foreshadowed from the beginning of the play in that people, the audience, hears what he has to say about the use of plants, how to mix them to create toxic formulas or dangerous combinations. The Friar’s plan needs to be executed on time. Not before, not after, because it has its reason. Juliette needs to be dead just for any specific time during the story. Romeo needs to know that Juliette is not really dead, but part of the plant, otherwise that could end in a tragedy.  

c) problem and solution

he is. some of his decisions were very irresponsible and did lead to the death of both romeo and juliet, such as him marrying them too quick or him not clarifying romeo's plan with him.

basically he did not think things through well enough or at all.

hope this