Final answer:
The U.S. withdrew support for Somoza's dictatorship in Nicaragua due to poor human rights policies, leading to the rise of the Sandinistas. The Reagan administration subsequently and covertly supported the anti-Sandinista Contras, despite congressional restrictions.
Step-by-step explanation:
Because the Somoza family's human rights policies did not improve in the 1970s, the United States, under President Jimmy Carter, withdrew support for the dictatorship. This shift in U.S. policy came as Carter sought to align foreign assistance with human rights considerations. The Somoza regime was eventually overthrown by the Sandinistas, a group of Marxist rebels. Contrary to options presented in the question, after President Ronald Reagan took office, the United States did not abstain from involvement. Instead, the Reagan administration, concerned about the Sandinistas' alignment with the Soviet Union and Cuba, covertly supported the anti-Sandinista forces known as the Contras, who opposed the Marxist government of Nicaragua. Despite the Boland Amendments, which intended to prohibit this support, the Reagan administration continued its covert aid, leading to the Iran-Contra scandal. The U.S. did not send troops to invade Nicaragua nor did the United Nations send peacekeeping forces to address human rights abuses during this period.