Answer:
It is called a noun clause
Explanation:
A clause that may be used as a subject complement is called a noun clause.
In the above excerpt Welty was using sensory details (principally sounds) to bring her story to life, She could hear her father shaving, and her mother cooking breakfast. She could hear the whispers and whistles and the clattering of shoes as she raced downstairs. She remembered he sound of the old Victrola. She could smell the bacon frying. Through all of these sensory impressions Welty has built a vivid and memorable picture of her childhood.
I believe it is B isn't, because if you use the others it most likely sounds like slang.
