Answer:
D.
"Whether the violence stops or not, it is likely that the country of Iran has changed forever."
Step-by-step explanation:
The question gives you the central idea: "The presidential elections in Iran in June of 2009 created one of the year's most important stories." This central idea is supported by the sentence, "Whether the violence stops or not, it is likely that the country of Iran has changed forever." If Iran really has "changed forever," then this is definitely a very "important story."