Which of the following in incorrect statement of the simple columnar epithelium :-

Options

A. It is composed of a single layer of tall and slender cells
B. Their nuclei are located at the base
C. Free surface may have microvilli
D. They are found in the walls of blood vessels and air sec of lungs

Answer

### Step-by-Step Solution:

1. **Understanding Simple Columnar Epithelium**:
- Simple columnar epithelium consists of a single layer of tall and slender cells. This is a defining characteristic of simple epithelium.

2. **Characteristics of Simple Columnar Epithelium**:
- The cells are typically taller than they are wide, resembling columns.
- The nuclei of these cells are usually located at the base of the cells.

3. **Presence of Projections**:
- The free surface of simple columnar epithelium may have projections. These projections can be either cilia or microvilli.
- Microvilli are commonly found in the gastrointestinal tract, while cilia may be present in respiratory tract epithelium.

4. **Identifying the Incorrect Statement**:
- The question asks for the incorrect statement regarding simple columnar epithelium.
- The correct statements include:
- It is composed of a single layer of tall and slender cells.
- The nuclei are located at the base of the cells.
- The free surface may have microvilli.
- The incorrect statement is that simple columnar epithelium is found in the walls of blood vessels and air sacs (alveoli). This is actually the characteristic of simple squamous epithelium.

5. **Conclusion**:
- Therefore, the incorrect statement about simple columnar epithelium is that it is found in the walls of blood vessels and air sacs.