An important property of air circulation is

a. warm air is denser than cold air.
b. cold air and warm air have the same density.
c. cold air is denser than warm air.
d. air has no mass.

How do oceanographers measure the salinity of ocean water?

In 2002, north korea announced that it was shutting down its nuclear facilities constructing a hydroelectric energy plant restarting nuclear weapon development changing to a free market economy

Pollution from one country can affect another. for example, south korea is especially affected by pollution and dust storms that come from