The West Cameroonian politician who played a major role in the abolition of the Federal system in favour of a unitary state was:

Here are the solutions to the questions:

25. The West Cameroonian politician who played a major role in the abolition of the Federal system in favour of a unitary state was: The transition from a federal system to a unitary state in Cameroon occurred in 1972. Salomon Tandeng Muna was a prominent West Cameroonian politician who served as the Prime Minister of West Cameroon and later as the Vice President of the Federal Republic of Cameroon, playing a significant role in this political development. The correct option is D. $\boxed{\text{D. S.T. Muna}}$

26. In which year did president Ahidjo officially inaugurate the National Oil Refinery Corporation (SONARA) in Limbe? The National Oil Refinery Corporation (SONARA) in Limbe, Cameroon, was officially inaugurated by President Ahmadou Ahidjo in 1981. The correct option is C. $\boxed{\text{C. 1981}}$

27. Which of the following was the most correct reason for the organization of Ghost Town Operation by some opposition parties? The "Ghost Town" operations (villes mortes) in Cameroon during the early 1990s were civil disobedience campaigns organized by opposition parties and civil society groups. Their primary aim was to pressure the government to introduce multi-party democracy and, most importantly, to organize a Sovereign National Conference to discuss the country's political future and draft a new constitution. The correct option is A. $\boxed{\text{A. To pressurize government to organize a sovereign National Conference}}$