The correct answer is D) imposing economic sanctions.
Congress tried to pressure South Africa into changing its apartheid system by imposing economic sanctions.
With this harsh measure, Congress tried to put pressure on the South Africa Government to end the injustices of the apartheid system. This created a positive effect and other nations also pressure the government of South Africa to end apartheid. In February 1990, Nelson Mandela was released from prison and things began to change until South Africa could have free elections in the mid-1990s.