Was there one Great Wall of China? Explain,

The Great Wall isn't a single wall at all, but a series of bulwarks and fortifications. The first went up some four centuries before Qin Shi Huang, who became China's first emperor in 221 BC, ordered a decade-long project to unite and expand these defences into a single barrier.

Explanation:

brainlist me^^

The Great Wall isn't a single wall at all, but a series of bulwarks and fortifications. The first went up some four centuries before Qin Shi Huang, who became China's first emperor in 221 BC, ordered a decade-long project to unite and expand these defences into a single barrier.

Explanation:

first, the romans stayed isolated because they had to defend their own territories from neighboring cities that were harassing them, like the etruscans. second, once the romans managed to defeat their neighbors, and started to expand their territory, they started to build roads and bridges. finally, now that the romans have covered their territory with roads functioning as highways, they could mobilize their legions faster to assemble larger military units in a specific place.

"choosing is refusing" means individuals face an opportunity cost with each decision they make. economists state that every decision involves trade-offs. opportunity cost is the least desirable alternative given up as a result of a decision.