A) the strength of women
When we look at Mattie we can see a woman who is strong because of all that she is and does throughout the novel. For instance, Mattie, in addition to being tough, is intelligent and entrepreneurial in a time when the characteristics of a woman were mainly weak, uneducated, and subservient. By encompassing not just one but many dominant characteristics, we see that women can not only equal men with regard to qualities, but can exceed them because of how much she does.
