What happens to the core of a star after a planetary nebula occurs?
A) It contracts from a protostar to a main-sequence star.
B) It breaks apart in a violent explosion.
C) It becomes a white dwarf.
D) It becomes a neutron star.
E) It can become either a neutron star or a black hole.
C) It becomes a white dwarf.
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Radioactivity Basics: A nucleus 
X undergoes one alpha decay followed by 3 beta-minus decays.(a) What is the resulting nucleus in terms of M and N?(b) If there had been 3 beta-plus decays instead of the beta-minus decays, what would have been the resulting nucleus in terms of M and N?
What will be an ideal response?
Earth's temperature remains fairly steady, which means that Earth must return nearly the same amount of energy to space that it receives from the Sun. In what form(s) does Earth return most of this energy to space?
a. infrared light emitted by the surface and atmosphere b. ultraviolet light reflected by the surface c. visible light reflected by clouds d. visible light emitted by the surface and atmosphere e. visible light reflected by the surface
Country X's population is doubling every 10 years. What is its rate of population growth?
A) It is impossible to answer this without knowing country X's population. B) 2% per year C) 7% per year D) 10% per year E) 14% per year
Determine the maximum altitude of the Sun on December 22 for an observer located at 30°N