Which phrase defines the time called prehistory? A. before computers
B. before the year 0
C. before written records
D. before the year 2000

Since pre means "before," and history is the record of human events, prehistory refers to the time before human civilization developed and started writing things down. Scientists often speculate about what happened in prehistory, which is also known as prehistoric times

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.

the answer would be in this answer. someone already asked the question.