What was the effect of Carter's attempts to free the hostages in Iran?
The hostages were returned to the United States immediately.
The United States increased its purchase of Iranian oil.
All of Carter's attempts failed.
The Sandinistas were overthrown.

The effect of Carter's attempts to free the hostages in Iran was that

All of Carter's attempts failed.

Explanation:

Operation Eagle Claw, known as Operation Tabas  in Iran, was a United States Armed Forces operation ordered by U.S. President Jimmy Carter to attempt to end the Iran hostage crisis by rescuing 52 embassy staff held captive at the Embassy of the United States, Tehran on 24 April 1980.The were several effects of Carter's attempts to free the hostages in Iran. These effects are as follows; -Even though he freed the hostages, they were returned to the United States immediately. - It lead to United States increasing its purchase of Iranian oilThe Iran Hostage Crisis, which lasted from 1979 to 1981, was the first time the United States was forced to deal with Islamic extremists. The students took action by seizing the United States embassy, which they saw as both a symbolic and tangible source of support for the Shah's authoritarian regime.All of Carter's attempts failed and this lead to the Sandinistas being overthrown