Final answer:
The action best described by the excerpt is the signing of the Magna Carta.
Step-by-step explanation:
The action best described by the excerpt is a) The signing of the Magna Carta. The Magna Carta was a historic document signed in 1215 by King John of England, which established the principle that the king was not above the law and that certain rights were guaranteed to the English people. It was a significant step towards limiting the power of the monarchy and establishing the rule of law.