Which of the following gives the two main assumptions of theoretical models of galaxy evolution?
A) Hydrogen and helium filled all of space, and the entire universe had exactly the same density everywhere.
B) The universe has always been expanding, and denser areas contracted to form the first stars.
C) Hydrogen and helium filled all of space, and certain regions of the universe were slightly denser than others.
D) The beginning of the universe is modeled after a supernova explosion, and all elements were produced by this exploding star.
E) The universe was composed originally only of hydrogen, and all the other elements came from stars.
C
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The length 3.76 mm is multiplied by 0.0232 mm. The appropriately rounded product is
A. 0.082 
B. 0.09
C. 0.087
D. 0.0872
E. 0.08723
For what slit separation will no 1st order double-slit-fringe appear for 550. nm light?
What will be an ideal response?
Which method relies on the mass of a dark object revealing its presence?
A) pulsars slowing down irregularly B) temporary brightening of a distant star by a gravity lens C) asteroidal occultations D) stellar eclipses E) ring occultations
When the Sun is located near one of the horizons, an observer looking at the sky directly overhead will view partially polarized light. This effect is due to which of the following processes?
a. double refraction c. selective absorption b. optical activity d. reflection