Answer:
Papa's agreeing to teach Sarah to ride a horse and drive a wagon develop a theme in Sarah, Plain and Tall which expresses the love and selflessness that exists in a family unit.
Explanation:
The central theme in Sarah, Plain and Tall is the family. As Papa agrees to teach Sarah to ride a horse and drive a wagon, we see that the this shows up the buildup of a complete family unit.
In the story, Papa, known as Jacob has been without a wife after his wife died. He was the only one taking care of his two children, Anna and Caleb and the farm. So, he made an advert asking for a wife and a mother. Then Sarah responded to the advert.
When Sarah came, she demanded to learn how to ride horse and drive wagon which Papa agreed to teach her. This builds up the existing theme of the family and expresses the love and selflessness the husband portrays to his wife.
