Final answer:
The Magna Carta, written in 1215, established the core idea of limited government and the belief that the monarch's rule was not absolute.
Step-by-step explanation:
The correct answer is a) Magna Carta.
The Magna Carta, written in 1215, established the core idea of limited government and the belief that the monarch's rule was not absolute. It was a document that limited the monarchy, established the guarantee of trial by jury, and protected the rights of the nobles and eventually all English citizens. The Magna Carta played a crucial role in shaping the concept of limited government and individual rights, which influenced the development of democratic systems in later centuries.