Why was trade important in medieval times? plz answer

Peoples, cities and states have traded since antiquity but in the medieval period, things escalated so that goods travelled ever greater distances by land, river and sea. Great cities arose thanks to commerce and international trade such as Constantinople, Venice and Cairo.

Explanation:

Correct answers:

A) the wheelbarrow

B) the suspension bridge

The Han Dynasty held power in ancient China from 206 BC – AD 220.  During that period, much progress was made by Chinese scientists/engineers in terms of practical technology.  In addition to items like suspension bridges and wheelbarrows (which we'll get to in a moment), the Han period also saw great advances in metallurgy, developing wrought iron and steel, as well as several tools for agriculture.

We think of the wheelbarrow as a tool we might use in our own backyard gardening and landscaping, but the one-wheeled cart  was developed during the Han period for a wide variety of hauling purposes.  

China's landscape includes deep gorges, rivers, and other obstacles best traversed by some sort of bridge.  During the Han period in China, they developed and built suspension bridges, as well as beam bridges, arch bridges, and pontoon bridges.