How does the author introduce and illustrate the differences between truly accidental discoveries and those made by hard working scientists?how does the author feels about two kind of discoveries luck favors the prepared

it depends on the natural disaster. a good one you can choose are hurricanes. water vapor is the "gas" and warm fronts are the "spark". because of the global warming that humans have caused with green house gases, hurricanes have become more frequent and stronger, making them more dangerous.

i think the answer is a

the correct answer is 3. her

this is so because the correct word to fill the gap is making reference to the subject "each of my sisters".

this subject is singurar due to the use of the word "each". although we have a group of people (sisters) mentioned here, the quantifier (each) singularizes the members of that group turning the subject into a singular one.

the word sister carries the female gender features.

so the referent should be singular in number and female in gender.