Answer:
Food Surplus
Step-by-step explanation:
The dragon backbone pump was a device used in china during the Song dynasty, to pump the water into canals to irrigate crops and to collect fresh water from wells. The unique thing about this device that even a single man could operate it. It was in use for almost 300 years. It was portable and advanced irrigation and farming became much easier by allowing one person to do the job of many. It helped to produce surplus food.