A Researcher Studying Small Town Religiosity in the United States

A researcher studying small town religiosity in the United States randomly selected ten states. From these states, he randomly selected one tenth of all counties. From these counties, he randomly selected one tenth of cities with populations smaller than 10,000. From these towns, he obtained lists of all houses of worship and randomly selected three. From these, he selected ten practitioners to be interviewed. In this example, which is not a cluster?

A) States
B) Counties
C) Cities with populations less than 10,000
D) Houses of worship
E) Practitioners