Relief is a sculptural technique where the sculpted elements remain attached to a solid background of the same material. The term relief is from the Latin verb relevo, to raise. To create a sculpture in relief is to give the impression that the sculpted material has been raised above the background plane.
Likely A, because if the costume hinders movement struggling in the costume could be unsafe.
Synonyms help us connect unknown words with known words. For example, one may not know the meaning of the word "nefarious" when used in this context: "The offense was more nefarious than previously thought." If we replace "nefarious" with "evil" or "wretched" the meaning is more comprehensible to those who don't know the meaning of "nefarious": The offense was more evil (wretched) than previously thought."
I hope this helps, I used nefarious as a somewhat uncommon term to better illustrate my point, and to explain why we use synonyms to learn new words. Simply put, synonyms bridge us to the unknown using the known as solid ground build from.