they lie in the same plane
Coplanar.
non-coplanar points are points that does not lie on the same plane... by:GRAETIA VILLANUEVA...
co-planar
collinear plane
No because only co-linear lines lie on the same plane
No, it does not.
No they can be Collinear - Points that lie on the same line.
the same line
Skew lines cannot lie in the same plane.
yeah
In general, yes. However, if there is a drawing that goes along with this question, and it shows more information about 'c' that you have not bothered to share, then it's certainly possible that point 'c' may not lie in the same plane as 'xy'.