According to our present theory of solar system formation, how did Earth end up with enough water to make oceans?
A) The water was mixed in the other materials in the planetesimals that accreted at our distance from the Sun.
B) The water was formed by chemical reactions among the minerals in the Earth's core.
C) The water was brought to the forming Earth by planetesimals that accreted beyond the orbit of Mars.
D) Earth formed in the relatively narrow region of the solar nebular in which liquid water was plentiful.
Question 2Space telescopes looking for transiting planets look for small drops in brightness; these drops are:
A) less than 10.
B) less than 1.
C) less than 0.01.
D) less than 0.0001.
E) any size.
Question 3A high-mass star dies more violently than a low-mass star because:
A) it must always end up as a black hole.
B) it generates more heat and its core eventually collapses very suddenly.
C) it cannot fuse elements heavier than carbon.
D) gravity is weakened by its high luminosity.
E) it is most often found as part of a binary system.
Question 4Life on Earth remained single celled for ________ years, according to the microfossil record.
Fill in the blank(s) with correct word
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