Which of the following is the hardest mineral?
a. Quartz
b. Diamond
c. Talc
d. Gypsum
b
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The ________ cycle of the phases of the Moon is due to the Moon's spherical shape and the ______ shining on it from different directions
a. monthly; Earth b. yearly; Earth c. monthly; Sun d. yearly; Sun
Series/Parallel Circuits: Two resistors having resistances of 5.0 ? and 9.0 ? are connected in parallel. A 4.0-? resistor is then connected in series with the parallel combination. An ideal 6.0-V battery is then connected across the series-parallel combination. What is the current through the 9.0-? resistor?
A. 0.35 A B. 0.53 A C. 0.83 A D. 0.30 A E. 0.67 A
Which of the following statements about rich clusters of galaxies (those with thousands of galaxies) is not true?
A) They are sources of X-ray emission due to the presence of hot, intergalactic gas. B) There likely have been numerous collisions among the member galaxies at some time in the past. C) Galaxies in the central regions are predominantly spirals, while elliptical galaxies roam the outskirts. D) They often have a very large, central dominant galaxy near their center, perhaps formed by the merger of several individual galaxies. E) The speeds of the galaxies in the cluster indicate that most of the cluster mass is dark matter.
Which of the following statements is true of interstellar dust?
A) It makes up about 10 percent of the mass of the interstellar medium. B) The average size of particles of interstellar dust is 1 micrometer. C) It is made mostly of carbon and silicates mixed with frozen water. D) It is uniformly distributed through space.