A(n) is a set of rules that determine what a layer would do and provides a clearly defined set of messages that software at the layer needs to understand.

Protocol.

Explanation:

As the exercise details, a protocol is a set of rules that determine what a layer would do and provides a clearly defined set of messages that software at the layer needs to understand. The word itself is related to a system of rules and acceptable behaviour. Therefore, the meaning of it in a corpus of programing is understandable.

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.

c: in the east might be the correct answer