The markers will expect something from Galvani, Davy and Faraday, since these three are specifically mentioned in the syllabus. IMHO, Volta is just there to connect the ideas of Galvani, and their relevance to Davy's work.
i.e. Volta identified that it was two metals in solution causing the trouble, and then he made the voltaic pile, which Davy used to decompose all his beverages.