The correct option is B muscularis
Gastrointestinal tract is divided into four layers such as mucosa, submucosa, muscularis and serosa.
The myenteric plexus or Auerbach’s plexus is in the muscularis layer of alimentary canal.
An inner plexus called the submucosal plexus or Meissner’s plexus lies in the submucosa.
Mucosa is the innermost layer and functions in absorption and secretion.
Serosa is the outermost layer and is made up of a thin mesothelium.