The primary purpose of the passage is to explain______.
A. the background and career of the astronomer Henrietta Leavitt
B. how and why various categories of stars vary in brightness
C. important uses of the camera as an astronomical tool
D. how a particular method of measuring astronomical distances was created
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Which of the following is NOT stated in the passage？
A. The process of species making chemical energy is similar to the process of combustion.
B. The process of species making chemical energy is less complicated than the process of combustion.
C. Fire is a portable, inanimate source of energy.
D. Man sometimes makes use of energy available in the bodies of stronger species.
When does the plane take off？
A. 4：15
B. 4：50
C. 4：55
How many guests are arriving？
A. 8
B. 6
C. 10
Which of the following did Leavitt's work provide astronomers with the means of determining？
A. The absolute brightness of any observable Cepheid variable.
B. The apparent brightness of any object at a given distance from an observer.
C. The distance from earth of any galaxy containing an observable Cepheid variable.
D. Both A and C
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