Which of the following serves as the cell's basic structural molecules or as enzymes that control chemical reactions?
A) Lipids
B) Proteins
C) Carbohydrates
D) Vitamins
B
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In outer space, you observe a straight stream of electrons flowing past you at 14.5 miles per second, about the same speed that Mars moves on its orbit around the sun. 
You maneuver your spacecraft to face the current so that the electrons are moving from left to right and so that you are 10 m from the stream. Now you fire your rockets and boost your speed so that you are also moving at 14.5 miles per second, exactly at the same speed and direction as the electrons. In what direction does a compass needle point now?
A. right 
B. down 
C. left 
D. up 
E. You observe no magnetic field
The atmosphere of Titan is chiefly
A) ammonia. B) nitrogen. C) oxygen. D) methane. E) hydrogen.
Standing Waves on a String: When a guitar is tuned to adjust it pitch, what is it that is changed?
A. The wavelength of the fundamental. B. The frequency of the fundamental. C. The amplitude of the fundamental.
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.