When the U.S. embassy in Iran was invaded and more than 50 Americans were taken hostage, how did the United States respond?

The Senate declared war on Iran and President Carter ordered troops to invade the country.
The United States chose to isolate itself and not get involved in the conflict.
The United States government purchased more oil from Iran hoping to convince them to release the hostages.
President Carter negotiated with Iran to have the hostages released.