Why did the U.S. support Saddam Hussein and Iraq in the war against Iran in the 1980s?

AThe U.S. considered Iran's militant Islam a bigger threat.
BIraq threatened to commit terrorist acts against the U.S. if the U.S. did not cooperate.
CThe U.S. wanted Iraq to conquer Iran and acquire control of the oil wells.
DAll answers are correct.

Verified Answer :

DThe US formerly supported the Christian Kingdom of Persia.  Ayatollah Khomeini seized power and turned it into an Islamic Republic. 
In the 1979, Iran held a bunch of ambassadors hostage.  This was very unpopular with the people and resulted in Jimmy Carter losing reelection. 
Iran was also very rich in oil, and the US wanted the valuable oil.