In the Sokoto Caliphate, the title Shehu (also rendered "Shaykh" or "Sheikh") was the honorific given to Usman dan Fodio, the founder and supreme spiritual and political leader of the caliphate. It designated him as the head of the entire Islamic state he established following the jihad of 1804.
The Sokoto Caliphate's political hierarchy distinguished several leadership roles. The Shehu stood at the apex as the overall leader. Beneath him, the caliphate was divided into two administrative halves: the western emirate governed from Gwandu (under a separate emir) and the eastern emirate governed from Sokoto. After Usman dan Fodio's death in 1817, his successors bore the title Sultan (or Sarkin Musulmi, "Commander of the Faithful"), while "Shehu" remained uniquely associated with the founding leader himself.
Among the options given, "the Caliph" most accurately captures the role. The Shehu was not merely an Imam (prayer leader), a war commander, or a district head. He was the supreme ruler of the caliphate, combining religious authority with executive political power across the entire state.
Exam tip: Remember that "Shehu" specifically refers to Usman dan Fodio and his role as the supreme leader (caliph) of the Sokoto Caliphate, not a subordinate title.