Answer:
The river floods, leaving fertile soil on the land.
The mythical Emperor Yu prevents the river from flooding again.
People can safely farm the fertile land near the river without fear of flooding.
Step-by-step explanation:
The river has to flood first for anyone to take notice and take action. After the Emperor prevents the river from flooding, people can use the benefits of the flood while avoiding potentially deadly consequences.
Hope this helps and good luck on your homework!