Epithelial cells usually form the outer or inner layer of tissues and organs. They are of several types, classified on the basis of their structure (morphology) and function.
Simple squamous epithelium (A) is a single layer flat cells (near a basal membrane) found where diffusion based activities are high.
Contrastingly, stratified squamous epithelium (B & C) is multiple layers of flat cells found adjacent to a basal membrane and they are found where there is a need to maintain structural integrity.
Therefore, options A, B and C are mismatched options and thus, incorrect.
Simple columnar epithelium (D) is found in those parts of digestive tract that is actively involved in digestion and absorption.
Therefore, option (D) is correct.