Some Breeds of Dogs That Are Specialized to Retrieve Objects

Some breeds of dogs that are specialized to retrieve objects from bodies of water have webbing between their toes. A change in what cellular response to positional information during digit formation could account for this morphological feature?

A) Signals that cause differentiation to toes are not received by cells that become webbing.
B) Signals to cause apoptosis are not received by cells that become webbing.
C) Cells between the future digits migrate, but do not divide once they are in the region that will become toes.
D) Cells between the future digits divide, but do not migrate to the region that will become toes.
E) Cells between the future digits do not divide before migrating to the region that will become toes.