Which statement regarding Nelson Mandela is accurate?

He was exiled from South Africa for most his life.
He was from Nigeria but led South Africa's anti-apartheid army.
He was elected South Africa's President after spending decades in jail.
He won the Nobel Peace Prize for helping prevent numerous terrorist acts in South Africa.

The accurate statement regarding Nelson Mandela is:

He was elected South Africa's President after spending decades in jail.

Nelson Mandela was indeed elected as President of South Africa in 1994 after having spent 27 years in prison due to his anti-apartheid activities. He was imprisoned for his leadership role in the African National Congress (ANC) and his involvement in the struggle against the policies of apartheid. He is also a Nobel Peace Prize laureate, but he received the prize in 1993 jointly with Frederik Willem de Klerk for their work in peacefully ending apartheid and laying the foundations for a democratic South Africa, not specifically for preventing numerous terrorist acts.