A noun is a person, place, or thing
I think A would be your best bet but im not 100% sure, space is a place and everyone I guess would be considered a person/people
B. It has a lighthearted affect on the conclusion that suggests the conflict has been resolved
The correct answer cannot be any of the other choices besides, sequence.
If the answer was "Adding an Idea" it would have to be furthermore, yet, in addition, and other choices.
The only category "Afterword" belongs in is a sequence.