Match the following vector fields with the verbal descriptions of the level curves or level surfaces to which they are perpendicular by putting the letter of the verbal description to the left of the number of the vector field.

 1. $\mathbf F = 2\mathbf i + \mathbf j$
 2. $\mathbf F = 2\mathbf i + \mathbf j + \mathbf k$
 3. $\mathbf F = 2x\mathbf i + y\mathbf j$
 4. $\mathbf F = x\mathbf i + y\mathbf j - z\mathbf k$
 5. $\mathbf F = x\mathbf i + y\mathbf j - \mathbf k$
 6. $\mathbf F = x\mathbf i + y\mathbf j$
 7. $\mathbf F = x\mathbf i + y\mathbf j + z\mathbf k$
 8. $\mathbf F = x\mathbf i - y\mathbf j$
 9. $\mathbf F = -\mathbf i + 0\cdot \mathbf j$
 10. $\mathbf F = y\mathbf i + x\mathbf j$
 11. $\mathbf F = 2x\mathbf i + y\mathbf j + z\mathbf k$

A. planes
B. lines
C. paraboloids
D. spheres
E. circles
F. hyperboloids
G. ellipses
H. ellipsoids
I. hyperbolas