Which characteristic of Earth explains why we have an ultraviolet-absorbing stratosphere?
A) the existence of photosynthetic life
B) the existence of plate tectonics
C) the moderate surface temperature
D) the existence of oceans
A
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Life is present on Earth because of oxygen
a. True b. False Indicate whether the statement is true or false
An old red star moving along a random orbit around the bulge is a
A. Pop I star. B. Pop II star. C. Pop III star. D. Pop V star.
Current estimates place the age of the universe at about
A) 10 billion years. B) 10 million years. C) 14 billion years. D) 4 billion years.
The potential energy of a spring is 0.25 J when it is compressed 0.04 m to the left of its equilibrium position. This is its leftmost position. What is its kinetic energy when it returns to the equilibrium point?
A. zero B. -0.3 J and moving to the left C. 0.3 J and moving to the right D. 0.3 J and at rest