Asecond plague invades the city of thebes and oedipus makes a declaration to find laius' murderer.
a climax
b rising action
c exposition.
d inciting incident

Don't quote me on this, but possibly B? 

(Definition of a rising action)
a related series of incidents in a literary plot that build toward the point of greatest interest. Compare falling action. Examples from the Web forrising action Expand. Yet there was the evidence: complex, developed characters; rising action ; conflict and climax; heroes and villains.