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 Iraqi Air Force dropped thousands of leaflets over Mosul on Saturday night to warn residents of a looming offensive on the ISIS-held city. "It's victory time," blares a headline on the newspaper-style leaflets, quoting Iraqi President Haider al-Abadi in remarks directed at Mosul's residents. "Time to celebrate a clean Iraq without 'Daesh' (ISIS) or any dark belief." Another headline reads, "We are preparing to take action to free Mosul and regain security and stability in the region." The four-page leaflets tell residents that coalition forces are making advances on Iraq's second-largest city and that no one should panic. Residents are asked to stay away from certain parts of the city, avoid ISIS positions, remain in their homes and seal their windows and doors. A phone number for Mosul residents to report ISIS activity is included.Iraqi military, Kurdish forces and other groups are preparing to retake MosulISIS tells its wounded fighters they can leave for Raqqa, Syria, a source says 
 Question:_ claimed responsibility for the attack in a statement released by the ISIS-affiliated Amaq Agency.

ISIS