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
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
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.