What were the most important tensions within the chinese cultural and social systems

Sailors went to special school to learn how to use the new technology that would them sail far distences. the school we know about was

The controlled use of fire by hominids: (a) limited the expansion of hominids into certain environments, such as dry grasslands. (b) decreased the amount of food energy available in the hominid diet. (c) contributed to geographical expansion and food production techniques in positive ways. (d) has been shown to contribute little to the digestive process of hominids.

Name that largest artificial lake built in the 11th century