Polybius Points Out That Government in the Roman Republic Was

Polybius points out that government in the Roman Republic was fundamentally different from government in any Greek city-state.What was this difference?

A) Rome had a completely professional army from an earlier period.
B) Roman government developed not from a set constitution but from trial and error to suit changing needs.
C) Rome had no element of a property-based class system.
D) Rome was always ruled by one man.
E) Roman government was created by written charter, and this charter was on display throughout the history of the Republic.