The water level in a lake has changed by -16.8 feet over the last 2.5 years. what is the average change in the water level each year?
a) -6.72
b) -0.672
c) 0.672
d) 6.72

Skew lines(segments) are lines(segments) in 3 dimensions that do not intersect the given segment and are not parallel to it.  ae, bf, eg, and fh are your skew segments.  i hope that : )