The correct answer is b) Stratified epithelium.

The epidermis is the outermost layer of the skin in vertebrates, and it is responsible for protecting the underlying tissues from damage, infection, and dehydration. It is composed of multiple layers of cells, known as epithelial cells. These cells are organized into different types of epithelium, including simple epithelium, stratified epithelium, transitional epithelium, and columnar epithelium.

Here, we will discuss each option and explain why stratified epithelium is the correct answer:

a) Simple epithelium: Simple epithelium is a single layer of cells that are tightly packed together. It is found in areas where absorption and secretion are the primary functions, such as the lining of the small intestine. However, the epidermis of the skin is not composed of a single layer of cells, so simple epithelium is not the correct answer.

b) Stratified epithelium: Stratified epithelium is a multi-layered epithelium, where the cells are stacked on top of each other. This type of epithelium is found in areas that experience high levels of mechanical stress, such as the skin. The epidermis of the skin is composed of several layers of cells, with the outermost layer being made up of dead cells called keratinocytes. These cells provide protection to the underlying tissues and help prevent water loss. Therefore, stratified epithelium is the correct answer.

c) Transitional epithelium: Transitional epithelium is a specialized type of epithelium that can stretch and contract. It is found in areas that need to accommodate changes in volume, such as the urinary bladder. The epidermis of the skin does not require this type of flexibility, so transitional epithelium is not the correct answer.

d) Columnar epithelium: Columnar epithelium is a type of epithelium where the cells are tall and column-shaped. It is found in areas where secretion and absorption are the primary functions, such as the lining of the stomach. The cells in the epidermis of the skin are not columnar in shape, so columnar epithelium is not the correct answer.

In conclusion, the epidermis of the skin is composed of stratified epithelium, which consists of multiple layers of cells that provide protection to the underlying tissues.