The author's central thesis is that A. the Navajo rejected the stylistic influences of Anglo culture B. Navajo weaving cannot be classified by Amsden's categories C. the Navajo changed their style of weaving because they sought the challenge of new artistic problems D. original motor habits and thought processes limit the extent to which a style can be revised E. the casual factors leading to the emergence of the bordered style are not as clear-cut as Amsden suggests