The following are the answers:
a. porous and permeable beds bounded on all sides by impermeable rock.
c. structural traps.
The opinions and prejudice of an author in writing.
I believe that those two elements greatly affect bias in history because we can never be 100% sure of everything that (may have) happened in history (especially farther in the past), so opinion can affect a historian's writings. Also, everyone is prone to some sort of prejudice, so this can also affect history.
In 1885 European leaders met at the infamous Berlin Conference to divide Africa and arbitrarily draw up borders that exist to this day. Lines of longitude and latitude, rivers and mountain ranges were pressed into service as borders separating the colonies.
Answer:
Floods are the country's number one natural disaster and happen throughout the country every year.