How Can We Tell That Some Stars Are Relatively Close

question 33

Multiple Choice

How can we tell that some stars are relatively close to us in the sky?

• A)Some stars are occasionally eclipsed by the Moon, so they must be nearby.
• B)Some stars vary in brightness caused by sunspots that we can see because they are so close.
• C)Some stars appear to be extremely bright and must therefore be very close to us.
• D)Some stars appear to move periodically back and forth against the background stars because of the Earth's movement around the Sun.

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Definitions:

Aging

The process of becoming older, a physiological and biological progression that involves changes in physical, psychological, and social attributes over time.

Free Radicals

Unstable atoms or molecules that have unpaired electrons, which can cause damage to cells, proteins, and DNA by oxidative stress.

Unstable Molecules

Chemical species with a short existence due to an inability to maintain a stable electronic configuration or structure.

Cells

The basic structural, functional, and biological units of all known living organisms.