Answer:
i think the answer is : PHTOTO
Explanation:
Sorry to bother, but you sent a invalid question, we don't know how to answer this unless you state what we are writing on.
This is math, not English, but okay xD
"Two intersecting lines are perpendicular if and only if they form four 90 degree angles" would be my answer.
Eery, spooky, quiet, silent, daunting, bristling, creaking