The Basque separatist organisation, known as the ETA, is active in Spain, not in Russia, Cyprus, or Portugal.

Option 1, Russia, is incorrect because the Basque region and its separatist movements are located within the borders of Spain, not Russia.

Option 2, Cyprus, is incorrect because Cyprus is a separate island nation located in the Mediterranean, far from the Basque region in Spain.

Option 3, Portugal, although sharing the Iberian Peninsula with Spain, does not contain the Basque region. Therefore, it is not where the Basque separatist organisation is active.

Option 4, Spain, is the correct answer, as that is where the Basque region is located physically and the separatist movement is operating. The ETA, which stands for Euskadi Ta Askatasuna (Basque Homeland and Liberty), is a Basque nationalist and separatist organisation that was active mainly in Spain.