Question

a radio telescope collects and amplifies *
○ light from the night sky
● radio waves
○ light wavelengths
○ popular tunes from the 80s

90 % of stars plot within the *
○ galaxy
○ known universe
● main sequence
○ night sky

Explanation:

First Question:

A radio telescope is designed to detect radio waves from celestial objects. Light from the night sky is detected by optical telescopes, light wavelengths are a property of light, and 80's tunes are irrelevant to astronomy. So the correct option is the one about radio waves.

The Hertzsprung - Russell diagram shows that about 90% of stars lie on the main sequence during their stable hydrogen - burning phase. Galaxies contain stars but the question is about star plotting, the known universe is too broad, and the night sky is just the visible part with stars but not the region where 90% plot.

Answer:

B. radio waves

Second Question: