Final answer:
China began overland trade with foreigners during the Tang dynasty, benefiting from a thriving economy and innovations that promoted interregional trade.
Step-by-step explanation:
China first started to trade over land with foreigners during the Tang dynasty, which lasted from 618 to 907 CE. During this period, China experienced significant economic growth, and trade flourished along the caravan routes, including the famous Silk Road.
Trade was not only in the hands of the state; it was also driven by the innovations and the interconnected market system that developed across the country. This era was marked by cultural achievements and technological innovations, such as paper-making and woodblock printing, which facilitated the spread of knowledge and trade.