How do these quotes from act 3 of Romeo and Juliet create suspense? (A)Prince: “Let Romeo hence in haste,Else, when he is found, that hour...

In his Prologue to Act I, William Shakespeare's Chorus
advises the audience of the "star-crossed lovers" who take their lives; consequently,
when the audience hears or sees lines such as those mentioned above, there is a certain
arousal of curiosity about how these contribute to the final outcome that has been
announced.

(A) This anticipation of tragedy is increased in
Act III as the climax,the highest point of intensity in the play.  In this act, Mercutio
and Tybalt encounter one another on a torrid day, and their tempers match the climate. 
As they insult one another Romeo comes on the scene.  Unfortunately, his attempts at
amelioration turn to fatality:  He slays Tybalt after Tybalt kills his dear friend
Mercutio.  Since the Prince has issued an edict that whoever revives the terrible feud
between the Capulets and the Montagues will have his own life forfeited--"Your lives
shall pay the forfeit of the peace" (1.1.70), the Prince offers Romeo a chance to save
his life by leaving Verona.  If, however, Romeo does not accept the banishment, he will
die.

(B) After Juliet has been told by her father that she
must marry Paris, she despairs because she is in a terrible quandary.  For, she has
already secretly married Romeo. If she tells her father that she is married, there will
be dire consequences, so she runs to Friar Laurence in her desperation.  Knowing the
predicament in which Juliet is, the audience wonders what she will do; of particular
concern are her words that suggest she contemplates
suicide.

(C) In Romeo's lines after he has slain Tybalt, he
knows of the terrible repercussions of his act.  He speaks of others' having to end the
sorrow that begins with Tybalt and Mercutio's deaths.  Clearly, suspense is created in
this instance as the audience wonders what further action will occur.  Among the
questions an audience may well ask themselves are these: What will both families do? 
What will become of Romeo's marriage to Juliet?

Always
throughout the play, Romeo and Juliet, an audience advised by the
words of the Prologue, wonder how the tragedy will be effected, and these lines
certainlly indicate the presence of a looming fate over the "star-crossed
lovers."