For capital letters, we can just add the ending -s, for example:
I got As in the final exam.
for lower-case letters, an apostrophe is used to avoid confusion:
In the multiple-choice exam all the correct answers happened to be a's! (as in: option a)
A protagonist is a character who evokes the reader’s sympathy.
Answer:
a verb os a person place or thing
I think the answer is When a solar flare erupts, it has the force of a hundred million hydrogen bombs. This is the answer because a bomb is dangerous and a solar flare is probably a type of fire thing cause by the sun so that makes the most sense and provides an example of a violent type of space weather.