The correct actions taken by the Carter administration in response to the Soviet Union's invasion of Afghanistan are:
1. Providing support to mujahideen fighters: The Carter administration provided covert assistance to Afghan mujahideen fighters who were resisting the Soviet invasion. This support included weapons, training, and financial aid to help them combat the Soviet forces.
2. Leading a boycott of the Moscow Summer Olympics: In response to the Soviet Union's invasion of Afghanistan, President Carter led a boycott of the 1980 Moscow Summer Olympics. The United States, along with other countries, refused to send athletes to participate in the games as a form of protest against the Soviet actions in Afghanistan.
These actions were significant steps taken by the Carter administration to respond to the Soviet Union's invasion of Afghanistan and to show opposition to Soviet aggression in the region.