About 90% of UFO sightings
A) are hoaxes
B) cannot be explained
C) are real sightings of alien craft
D) can be explained by natural phenomena
D
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Which of the following correctly describes what we mean by a great circle on the surface of Earth?
A) any circle of latitude B) any circle whose center is at the center of Earth C) any circle larger than 10,000 km in diameter D) a circle of longitude
In age, Population I stars are typically much ________ than those of Population II
Fill in the blank(s) with correct word
Ridges in the middle of the ocean are places where
A) one plate slides under another, returning older crust to the mantle. B) hot mantle material rises upward, creating volcanic islands. C) hot mantle material rises upward and spreads sideways, pushing the plates apart. D) plates push together, creating ocean mountain chains. E) plates slip sideways relative to one another.
The planet COROT-14b is only slightly larger than Jupiter, but is several times more massive. Which is the most plausible explanation for its similar size to Jupiter?
A) Planets that are close to a star are heated up and therefore larger. B) The mass measurement is mistaken, and it is actually about 10 times more massive than Jupiter. C) It is made of elements other than hydrogen and helium which do not compress under their own gravity. D) The hydrogen and helium gas compressed even under their own gravity to a higher density than Jupiter.