What are the gases that come to equilibrium between the upper layer of the ocean and the atmosphere?

What is the approximate circumference of the circle shown below? 12.2 cm

Which of the following describes what rocks usually are composed of ,

The world wars of the twentieth century immediately led to a. the establishment of a communist bloc in eastern europe b. the urbanization of europe’s societies c. an emphasis on humanism d. an emphasis on ties to greek and roman societies select the best answer from the choices provided. a b c d