听力原文： The Shell oil company says villagers in the south-eastern part of the country have released the last of the more than 100 hostages they seized Saturday. The hostages are Nigerian employees of the Shell oil company. They were seized by the Ejaw ethnic group in Delta state. The hostages were seized to protest a decision by Nigeria's government to place a new municipal council in the territory of the opposing ethnic group. The dispute does not involve Shell oil company's policies.
Who held the hostages？

A. Workers of the Shell oil company.
B. Nigerian officials.
C. Villagers of an ethnic group in Nigeria.
D. Managing staff of the Shell oil company.