Seyfert galaxies
a. are more common in close pairs of galaxies than in isolated systems.
b. emit more energy at X-ray, ultraviolet, infrared, or radio wavelengths than normal spiral galaxies.
c. generally show redshifts greater than 6.
d. are more common in close pairs of galaxies than in isolated systems and emit more energy at X-ray, ultraviolet, infrared, or radio wavelengths than normal spiral galaxies.
e. are more common in close pairs of galaxies than in isolated systems; emit more energy at X-ray, ultraviolet, infrared, or radio wavelengths than normal spiral galaxies; and generally show redshifts greater than 6.
Question 2
The lowest-mass stars cannot become giants because
a. they do not contain helium.
b. they rotate too slowly.
c. their convective interiors prevent the development of an inert helium core surrounded by unprocessed hydrogen.
d. they contain strong magnetic fields.
e. they never use up their hydrogen.
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