Which of the following did carter do to free the hostages in iran?
carter sought from the soviet union.
carter freed up billions of dollars of iranian assets.
carter refused to buy any iranian oil.
carter convinced us allies to invade iran.

To free the hostages in Iran, President Carter refused to buy any Iranian oil.

After his overthrow, the Shah was allowed to travel to the USA to receive medical treatment. The Islamist rebels demanded the United States to extradite the Shah back to Iran to try him for crimes committed by his government during his reign over ordinary citizens with the help of his secret police, the SAVAK. In Iran, the asylum granted by the USA for the Shah it was seen as an act of complicity.

Carter refused to yield to the demands, Khomeini used the situation to consolidate his power and nullify the challenges of the moderate wing of his government, headed by its president. The euphoria over the humiliation of the most powerful nation distracted the Iranian people from the economic difficulties of their country. Carter, in April 1980, broke diplomatic relations with Iran and imposed a trade embargo, except medicine and food. Iranian funds in the US were frozen and accounted for to compensate the hostages when they were released and to pay the demands of US companies against Iran.