The appositive is a renaming of a noun, something that can be skipped without changing the grammatically and meaning of the sentence.
Here the appositive is "Dr. Walters" - it can be skipped:
My dentist was one of the speakers at Career Day
and it renames "My dentist" - answer B
Assuming this is still referring to Hemmingway's style, the proper terms would be theme and description, although he was known a lot for his simplicity as well.
A sounds the most grammatically correct
Yes how do you want me to do it
Lennie started petting a lady's dress and scared her
