Which statement about our current knowledge of elements is FALSE?
A) We now know of more than 110 elements, both natural and man-made.
B) 81 stable elements have been found on Earth.
C) 10 radioactive elements are also found on Earth.
D) We have now produced over 50 radioactive elements not occurring in nature.
E) Technetium is found in giant stars, but not yet in nature on the Earth.
D
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Star X has a smaller parallax angle than star Y. What can you conclude?
A) Star X is nearer to Earth than star Y. B) Star X is farther from Earth than star Y. C) Star X is more luminous than star Y. D) 10 Star X is less luminous than star Y. E) Star X is smaller in radius than star Y.
A 100-W lamp glows brighter than a 25-W lamp. The current drawn by the 100-W lamp is
A) less. B) greater. C) the same.
When water at 0°C freezes, the entropy of the water
A) increases. B) decreases. C) remains constant. D) could either increase or decrease; it depends on other factors.
The theory that Mercury shrank slightly when it was young has been proposed to explain
a. extended lava plains. b. large craters. c. magnetic field. d. lobate scarps. e. regolith.