The greenhouse effect occurs on Earth because carbon dioxide is
a. transparent to visible light and opaque to infrared radiation.
b. opaque to visible light and transparent to infrared radiation
c. totally opaque to both visible light and infrared radiation
d. totally opaque to both visible light and infrared radiation
Question 2Old stars are poor in heavy atoms because there were very few previous generations of stars before the old stars formed.
Indicate whether the statement is true or false
Question 3The oxygen in Earth's atmosphere
a. was manufactured inside stars.
b. was added to the atmosphere by plant life.
c. has grown more abundant since the origin of Earth.
d. all of these
e. none of these
Question 4The rapid rotation in the outer disk suggests that our galaxy is more massive than previously thought.
Indicate whether the statement is true or false
Question 5Which of the following is not produced by plate tectonics?
a. midocean rifts
b. rift valleys
c. the ring of fire
d. the Appalachian Mountains
e. Earth's magnetic field
Question 6The disk of the Milky Way is approximately 20,000 ly in diameter.
Indicate whether the statement is true or false
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