Hale discovered that sunspots were associated with magnetic fields. What happens to these magnetic fields during a full sunspot cycle?
A) They change polarity. B) They get weaker.
C) They get stronger. D) They die away.
A
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To reduce energy waste, we must
A. increase energy consumption. B. improve energy efficiency. C. switch from fossil fuels. D. use only solar technologies. E. lower energy efficiency.
What is the approximate length of time preserved in Grand Canyon rocks?
a. 10,000 years b. 100,000 years c. 1 million years d. 1 billion years e. 10 billion years
The fact that Japan is so well developed indicates
A. comparative advantages that do not include natural resources. B. abundant natural resources. C. strategic advantages unavailable to other east Asian countries. D. that Japan is less dependent on imported energy than China.
The gaseous oxygen in the Earth's atmosphere was produced as a by-product of
A) volcanic outgassing. B) photochemical reactions breaking down ozone (O3 ) to form oxygen (O2 ). C) photosynthesis. D) decay of organic matter.