A flashback is when something is remembered from the past. And a flash forward is when you like make a video go to like the next seen or something like that.
Please do not take my word on this because i am no 100% sure but i think it is B because he is using a metaphor to compare his life to crystal stairs.
Answer:
The action of moving back and forth quickly and steadily.
The 3rd one is the answer
Historical because he is comparing one first to another first in history so that means its historical.
