b. A reliable food production and distribution system
Explanation:
The Tang and Song Empires were successful at creating increased food production. Irrigation systems were responsible for more growing areas and particularly helped produced more rice. The empires also manipulated the landscape to create more land to farm. Terrace systems within the land also increased the amount of land that could be farmed at any one time. Cotton, tea, and rice became the most produced crops making money for the empires.
At its highest point, the vertical velocity is zero. As the object falls toward Earth again, the vertical velocity increases again in magnitude but points in the opposite direction to the initial vertical velocity.
