Why is it thought that quasars probably spend only a fairly short time in their highly luminous phase?
A) because there aren't many quasars around today
B) because there aren't any quasars closer than about a redshift of 1
C) because all quasars are at about the same epoch, narrowly defined in time
D) because a black hole could not power a highly luminous quasar for more than a few million years
E) because quasars are known to be the consumers of massive galaxies
D
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Indicate whether the statement is true or false
Current evidence suggests that the Universe is
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