Question

fff: repairing 3d files
use the information below to answer the question.
sometimes when going from 3d modeling to the printing software, there is geometry
that isnt quite right. this needs to be adjusted or changed in order to print. there are
software programs that can be downloaded for free to clean up a file to get it ready
for printing. the software often includes editing tools as well. the software will flip
or reverse the normal. in geometry, a normal refers to two elements that are at 90
degrees to each other. if the geometry is facing out, it needs to be flipped in. the
object also needs to be watertight. there cant be any holes or missing pieces in the
mesh. it must have a continuous geometry all the way around. (this does not refer to
holes that have been designed in.)
in geometry, what does a
ormal\ refer to?
the x axis of a designthe y axis of a designtwo elements that are parallel to each othertwo elements that are at 90 degrees to each other

Explanation:

The text explicitly states that in geometry, a normal refers to two elements that are at 90 degrees to each other.

Answer:

two elements that are at 90 degrees to each other