Some people obtain their water from underground layers of rock or sediment called .

aquifers

Explanation:

It's a naturally occuring underground layer of rock, gravel, sand or even salt that contains a lot of water. This is enough to provide a lot of water supply that people can use.

aquifers

Explanation:

Some people obtain their water from underground layers of rock or sediment called aquifers. It's a naturally occuring underground layer of rock, gravel, sand or even salt that contains a lot of water. This is enough to provide a lot of water supply that people can use

reflecting point a across the origin negates both of its coordinates.

b = (5, -4)