Why did students occupy the U.S. embassy on November 4, 1979?

The reason most often given for the student occupation of the embassy was that the United States was allowing the Shah to enter the USA, rather than returning him to "face justice" in Iran. But there were other reasons: poor management of the issues by President Jimmy Carter, a history of Iranian resentment against American interference in Iran, (truthful) claims that the embassy was being used for espionage, Ayatollah Khomeini approving the occupation for his own political purposes and the students being radicalised by religious leaders. This source-based task is designed for students of the NSW Modern History Syllabus for the Australian Curriculum.
Higher school Certificate course
National Studies
Option H: Iran 1953-1989