The correct option is A squamous epithelium
On the basis of structural modification of the cells, simple epithelium is further divided into three types. These are - (i) squamous, (ii) cuboidal and (iii) columnar.
The squamous epithelium is made of a single thin layer of flattened cells with irregular boundaries. They are found in the walls of blood vessels and air sacs of lungs (alveoli) and are involved in a functions like forming a diffusion boundary.