Option 1, Switzerland: It is incorrect. Switzerland is known for a unique system of government where the head (President) changes every year and is chosen among the seven members of the Swiss Federal Council.
Option 2, Cuba: This is the correct answer. Fidel Castro, the former prime minister and president of Cuba, held the power for over 49 years (1959-2008). Considering also his period as First Secretary of the Communist Party of Cuba (1965-2011), this sets him up as one of the longest ruling leaders.
Option 3, Zimbabwe: Robert Mugabe was Zimbabwe`s head of government for 37 years, which is less than Castro`s tenure.
Option 4, New Zealand: It is incorrect. New Zealand has a democratic system where governments change frequently with elections held every three years.
In conclusion, Fidel Castro of Cuba was the world’s longest ruling head of government.