Answer to Question 1
Light pollution is the brightening of the night sky by light scattered from artificial outdoor lighting. Light pollution can make it impossible to see faint objects. In fact, many residents of cities are unfamiliar with the beauty of the night sky because they can see only the brightest stars. Radio astronomers face a problem of radio interference analogous to light pollution. Weak radio signals from the cosmos are easily drowned out by human radio interference-everything from automobiles with faulty ignition systems to poorly designed transmitters in communication. To avoid that, radio astronomers locate their telescopes as far from civilization as possible. Hidden deep in mountain valleys, they are able to listen to the sky protected from human-made radio noise.
Answer to Question 2
D