¿Qué cadenas montañosas sirven como fronteras naturales en Europa?​

Where is the map? it's not showing

Primary sources are usually  more accurate and are written by someone who experienced it or witnessed it. secondary sources are those who heard of it after the fact that can lose details and or twist the event in a light that benefits them.

The correct answer would be : a system of classes that were organized like a pyramidi hope that this you !