Question

after returning to south africa from algeria in 1964, nelson mandela was
arrested and imprisoned.
elected to the presidency.
educated in guerrilla tactics.
finally granted his freedom.

Explanation:

Nelson Mandela was arrested in 1962, put on trial, and sentenced to life imprisonment in 1964. He was elected president in 1994, trained in guerrilla tactics before 1964, and freed in 1990. The event matching 1964 is his imprisonment after arrest.

Answer:

arrested and imprisoned.