Why are ores so valuable?
A) They are sources of naturally occurring gold.
B) Metals can be efficiently extracted from them.
C) They tend to occur in scenic mountainous regions.
D) They hold many clues to Earth's natural history.
Answer: B
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Indicate whether the statement is true or false
Consider a student whose mass is 70 kg. If all his mass were converted to electrical energy, for how many years could he keep a 100-W light bulb burning?
(c = 3.0 × 108 m/s)
In general, warm days are associated with
A) high surface pressure. B) low surface pressure. C) summer storms. D) negative change in pressure gradient.
A flat coil is in a uniform magnetic field. The magnetic flux through the coil is greatest when the plane of its area is
A) parallel to the magnetic field. B) at 45° with the magnetic field. C) perpendicular to the magnetic field.