I'm not really sure what specific answer they're looking for, but if it's an open-ended question, then let's think about it this way...
A light year, is the distance it takes for light to travel in a year. If an object is 50,000 light years away, then by the time the light travels to us, 50,000 years has passed. We are looking at a 50,000 year old image of that object. (ignoring gravity and spatial expansion fun stuffs)
<span>A magnetic field would be produced by a beam of (3) protons.
Although you could easily make a case for any of these four options (the question is pretty ambiguous), there can be only one correct answer, which is the third option, in this case.
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A. Lowering the temperature.
You could talk about how the planets spin around the sun, how the universe has galaxies, and we are in the milky way. Blue shift and red shift,etc?
The answer to this question is A.