The excerpt from the selection that best helps you to visualize Mrs. Pratchett is - "...Mrs. Pratchett's skinny goat's legs trotting to keep up with him. So, the Option D is the accurate answer.
<u>Explanation</u>:
In Roald Dahl’s “Boy: Tales of Childhood,” is a medium through which he recalls his school days and the pranks he played during his young age. Mrs. Pratchett is a character found in his autobiography and was the owner of a sweet shop. She was described as a mean, small, dirty, skinny lady with a moustache. Her apron was greasy and grey in appearance. Her blouse had marks of breakfast on it. Her hands were dirty and full of grime. Plus, she had goat-like legs. All these adjectives give the reader an idea about how Mrs. Pratchett actually looked.
Stream of conscious narration is an example of experimentation in American modernism. The other techniques were commonly used long before the advent of modernism and would not be examples of experimentation.