Why must lander probes on Mars be sterilized before launch?
A) to prevent terrestrial microbes hitching a ride on the probe and contaminating the Martian surface
B) to prevent terrestrial microbes destroying the electronics in the probe during its passage to Mars
C) to prevent Martian dust from building up on the probe on the surface
D) to prevent Martian microbes from contaminating the lander probe
A
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Which type of force would be the equal and opposite force to a gravitational force?
A. gravitational B. electromagnetic C. strong D. weak E. It could be any one of the above or some combination of them.
One ancient Greek scientist, Aristarchus, had a theory about the layout of the universe that was quite different from the other Greek theories. According to Aristarchus's theory,
A) Earth is at the center and other objects move around Earth in simple circles. B) the sun is at the center and other objects, including Earth, move around the sun in simple circles. C) Earth is at the center, and the planets move around Earth in orbits that could be described as "circles-within-circles" or "loop-the-loops." D) the Earth is held up by Hercules, who stands on a turtle, who stands on an elephant, who stands on Zeus, who is beginning to think that the whole thing isn't worth the effort. E) there is no fixed center anywhere in the universe.
A type of cloud composed of ice crystals is the
a. altostratus. b. cirrostratus. c. stratus. d. nimbostratus.
Metallic bonding is caused by
A) the sharing of electrons by all atoms. B) the transfer of electrons between atoms. C) unequal charge distributions around neutral molecules. D) atoms bonding to hydrogen molecules. E) atoms bonding to oxygen molecules.