Which of these is a factor in the U. S. need to find alternative energy sources?
A. Finite oil reserves and an expanding market for oil
B. A decrease in population
C. Poor corn harvests in lowa
D. The environmental impact of windmills

A. Finite oil reserves and an expanding market for oil

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.

agriculture revolution