Shark : fish :: koala : bear
At least I think it is because a shark is a fish so I guess a koala is to bear.
I hope I helped :)
Answer:
Familiar
Explanation
In the passage your brain are what tiggers your memories to appear when something familiar is seen.
A is an easier topic. B is harder but both are interesting.
This person is a hardcore night owl if they stay up all night to do the work