Large meteoroids are thought to collide with Earth:
A) at least once a decade.
B) about once a century.
C) a few times in every million-year period.
D) once every billion years.
E) never; only comets are thought to collide with Earth.
C
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The ignition of helium in the core of a star changes the structure of the star. The star now makes energy in two locations by two different processes, _____
A) carbon fusion in the core and helium fusion in the surrounding shell B) helium fusion in the core and nitrogen fusion in the surrounding shell C) helium fusion in the core and hydrogen fusion in the surrounding shell D) nitrogen fusion in the core and helium fusion in the surrounding shell
Stars in the upper right part of the Hertzsprung-Russell diagram are always ____ when compared to stars near the middle of the diagram
a. cooler b. brighter as seen from Earth c. larger d. smaller e. more massive
Density: Substance A has a density of 3 g/cm3 and substance B has a density of 4 g/cm3. In order to obtain equal masses of these two substances, what must be the ratio of the volume of A to the volume of B?
A. 
= 
B. 
= 
C. 
= 
D. 
= 
E. 
= 
In a double-slit experiment, if the slit separation is increased, which of the following happens to the interference pattern shown on the screen?
A) The minima get closer together. B) The maxima get further apart. C) The minima stay at the same position. D) The maxima stay at the same position. E) The minima and maxima stay at the same position.