Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: (CNN)The Pentagon's recent statement that Iran may have conducted air strikes against ISIS targets in Iraq's Diyala Province is tantamount to a U.S. tacit approval of Iran's growing military footprint in Iraq. No military operation of such scale evades detection from U.S. radars. Even if not pre-approved or coordinated, Iran's air and ground operations against the murderous thugs of self-proclaimed caliph Abu Bakr al-Baghdadi make the Islamic Republic effectively a U.S. partner in the fight against America's greatest enemy: Islamist fundamentalism. The U.S. strategy towards the Middle East since the Arab Spring has been defined by proactive disengagement and hesitance.The U.S. strategy towards the Mideast has been disengaging, writes Andreas KriegPresident Barack Obama increasingly appears to be the lame-duck, he writesKrieg: Good cooperation with Tehran allows the U.S. to put pressure on its Arab partnersAmerica's credibility as a superpower is in doubt, he says 
 Question:The broadcasted images of _ citizens being brutally beheaded in front of a global audience shook America to its core.

U.S.