To maximize character animation quality, each vertex of a 3D mesh should be mapped to:

A.
opaque textures.

B.
multiple bones.

C.
a single bone target.

D.
proximity triggers.

Explanation:
http://mobilebits.de/Blog/post/2007/02/25/Skeletal-Bone-Animation-and-Skinning-withCollada-Models-in-XNA.aspx