A. allowing them to take control of the trade with the hinterland
B. replacing Indian middlemen with Europeans
C. allowing European consuls to reside in Zanzibar
D. making English the lingua franca of Zanzibar.
Correct Answer: Option C
C. allowing European consuls to reside in Zanzibar
Explanation
The European consuls were to ensure compliance with commercial treaties signed between their countries and the Omani rulers and to protect citizens of their countries from molestations.