How did Emperor Shihuangdi began the construction of the Great Wall of China?

Atown is built on the banks of a small lake on the edge of a desert. after some time, the townspeople discover that water from the lake has become too polluted to use. describe one way that the lake may have been contaminated by the actions of the townspeople, and explain how the townspeople can remediate this problem.

There is only one climate type in motion across the world at a time

Which season occurs in the northern hemisphere when the sun is at its lowest point in the sky