Why does the author include this description?

to explain why humans cannot see X-rays
to explain how X-rays help scientists study space
to explain that black holes are extraordinary
to explain where black holes are located

How to prevent onions from making you cry chill the onions in the refrigerator for 30 minutes before peeling or chopping them. sulfuric vapors move slower in the cold—think about how garbage smells worse during hot weather. leave the onion root intact until the last possible moment to prevent irritants from escaping into the air. the root contains the largest concentration of sulfuric compounds in an onion. chop or cut the onion with a sharp knife. fast, clean slicing puts less pressure on the onion tissue and minimizes the release of sulfuric compounds. a sharp knife also allows you to expedite your slicing and reduce your exposure to the onion fumes. open a window or light a scented candle close to your chopping station. the hot flame of a candle will attract tear-causing vapor and will reduce the amount of vapor circulating in the air. what can be done to these instructions to make them easier to read at a glance? deleting everything except the first sentences of each numbered step eliminating the numbers and using bullets using illustrations instead of text changing nothing

What is frankensteins main goal after he sees the monster for the first time

How do i can change this sentence : a modern physician in a small town not only is proficient in general medicine but surgery as well. to parallel structure?