What is the serosa? a. the outermost of the two middle layers of the wall of the gi tract b. the outer layer of the wall of the gi tract c. the innermost of the two middle layers of the wall of the gi tract d. the inner layer of the wall of the gi tract

The correct option is A.
The serosa refers to the outermost layer of loose connective tissues which is often covered by mucus and which contains blood vessels. In the gastrol intestinal tract, the serosa refers to the outermost layer of the wall of the GI tract. One major function of serosa is to reduce friction from muscle movement.