C is the correct answer. All of the attempts were failed.
In April 1980, frustrated with the slow pace of diplomacy (and over the objections of several of his advisers), Carter decided to launch a risky military rescue mission known as Operation Eagle Claw. The operation was supposed to send an elite rescue team into the embassy compound. However, a severe desert sandstorm on the day of the mission caused several helicopters to malfunction, including one that veered into a large transport plane during takeoff. Eight American servicemen were killed in the accident, and Operation Eagle Claw was aborted.
President Carter continued to attempt to secure the hostages' release before his presidency's end. On 20 January 1981, minutes after Carter's term ended, the 52 US captives held in Iran were released, ending the 444-day Iran hostage crisis.
