During the Cenozoic, animals grew to great sizes and proportions. The woolly mammoth and the saber tooth tiger were much larger than animals we see today. Some of the causes for their extinction may be
A) the emergence of man and competition for food.
B) burning of the grasslands, severe climatic change, and man's emergence.
C) dwindling food supplies, extreme climatic variation, and man's emergence.
D) the extensive ice sheets that covered the land surface.
Answer: C
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All the following statements are true. Which one can be attributed to the exclusion principle?
A) Two electrons with the same spin cannot occupy the same energy level in an atom. B) If we know the location of an electron quite well, we will have little idea where it is going next. C) If an electron and antielectron meet, they will turn into energy through mutual annihilation. D) An electron has energy equal to its mass times the speed of light squared.
Which of the stars in the diagram has the largest absolute visual magnitude?
Consider a two-slit interference experiment like the one shown in figure Q3.7b. The distance between adjacent bright spots in the interference pattern on the screen (A) increases, (B) decreases, or (C) remains the same if, The distance between the slits and the screen increases.
A. increases B. decreases C. remains the same
How do we determine the conditions that existed in the early universe?
A) We work backward from current conditions to calculate what temperatures and densities must have been when the observable universe was much smaller in size. B) We look all the way to the cosmological horizon, where we can see the actual conditions that prevailed all the way back to the first instant of the Big Bang. C) The conditions in the very early universe must have been much like those found in stars today, so we learn about them by studying stars. D) We can only guess at the conditions, because we have no way to calculate or observe what they were.