This is the correct answer just took the test.

How is coal extracted from mountaintop removal mines? a. dynamite is used to create underground tunnels where miners go to extract the coal. b. dynamite is used to break apart rocks and then draglines are used to remove the broken rock and reach the coal. c. coal in mountaintops is extracted by digging strips in the landscape to reach the coal. d. placer deposits in mountain river bottoms are removed by

At very high pressures, gases become and will eventually a) more dense; become hotter b) more dense; change to a liquid or solid c) less dense; combust d) less dense; turn into a liquid

You've already seen the value of 9.8 in this lesson. what's this value called? what quantity does it represent?