Think back to your knowledge of the carbon cycle. Some human activities increase the levels of CO2 in the atmosphere. In which year does CO2 concentration seem to make a pivotal turn? What are some human activities that could have influenced CO2 levels in this period?

How is the composition of a meteorite relevant to finding out the composition of earth's core?

Provide a stepwise curved arrow mechanism that fully explains the outcome of the reaction shown below. oh нао* heat он

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.