Question: What kind of group does Birmingham City F.C. and English football league system have in common?
Sentence (from "English football league system"): The system has a hierarchical format with promotion and relegation between leagues at different levels, allowing even the smallest club the theoretical possibility of ultimately rising to the very top of the system, although in practice it would take a team at the bottom levels at least two decades of consistently finishing at or near the top of each successive league to reach the top level, and even then additional restrictions, particularly in regard to stadium facilities, would then come into effect at the highest levels that could prevent a club from being allowed access to the top levels.
Relevant evidence: No