What is the fundamental facilities and systems serving a country, city, or area, such as transportation and communication systems, power plants, and schools called

i am pretty sure the awsers is d.

music

explanation:

1. it was caused by feudalism

2. charlemagne used christianity as a major cornerstone for his rule. cloisters were built all over the empire to act as centers for the (re)population of the vast european wilderness.

3. the europeans feared the next raid every time chetak

i'm not so sure about #6. but i hope i you with the first 3.