Answer:
The correct answers are:
A. Irrigation systems were improved.
C. Crop rotation was introduced.
D. He replanted trees.
Step-by-step explanation:
Zhu Yuanzhang came from a peasant family, so he knew how peasants suffered and he knew their needs. Also, due to the reduction of trade and commerce, agriculture became the focus of economic policy. In order to improve it, projects like irrigation systems were improved to help farmers. The emperor also planted more than 50 million trees in the region of Nanjing, and along with rice terraces, he also introduced crop rotation: new crops like sweet potatos, peanuts and tobacco were planted and changed the diet and the use of cash crops.