When chemists say that a planet's upper regions are reduced, they mean that these regions
A) have far less material than other parts of the planet
B) are dominated by the element oxygen and its compounds
C) are so warm that no molecules can exist
D) are dominated by the element hydrogen and its compounds
E) have been bombarded over the years by many asteroids, causing large craters on the surface

Question

Quizplus · Accepted Answer

When chemists say that a planet's upper regions are reduced, they mean that these regions are dominated by the element hydrogen and its compounds, which have low levels of oxygen. Therefore, the best choice is D.

When Chemists Say That a Planet's Upper Regions Are Reduced