The correct option is C A plane
Let →r be also represented in the form of three non-coplanar vectors →a,→b,→c.
Let →r=x→a+y→b+z→c
Hence, x→a+y→b+z→c=(1−p−q)→a+p→b+q→c
Comparing RHS to LHS gives us
x=1−p−q
y=p
z=q
Then x=1−y−z
x+y+z=1
This represents an equation of a plane where the co-ordinate axes are →a, →b and →c, and also the plane does not pass through origin.