Match the surfaces with the verbal description of the level curves by placing the letter of the verbal description to the left of the number of the surface.
1.
2.
3.
4.
5.
6.
7.
A. a collection of equally spaced parallel lines
B. a collection of equally spaced concentric circles
C. two straight lines and a collection of hyperbolas
D. a collection of unequally spaced concentric circles
E. a collection of unequally spaced parallel lines
F. a collection of concentric ellipses