Which of the following is a threat to the ozone layer?
A) coal burning
B) freon refrigerants
C) Both of the above.
D) automobile exhaust
E) None of the above.
B
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The image of a convex mirror is always
a. virtual, inverted, and larger. b. virtual, upright, and smaller. c. real, upright, and smaller. d. real, inverted, and larger.
Unlike the ultraviolet photons originally emitted by the embedded stars of an emission nebula, the photons emitted by the recombination of electrons with atoms:
A) do not escape the nebula. B) escape the nebula. C) are re-absorbed by neutral hydrogen atoms. D) bounce around inside the nebula. E) are scattered by the dust particles.
The mass of the black hole in the center of the galaxy has been determined by observing the motion of stars orbiting it
a. True b. False Indicate whether the statement is true or false
When you compress air with a tire pump, the air temperature in the tire
A) increases. B) decreases. C) remains unaffected. D) none of the above