Epithelium is connected to underlying connective tissue by

The correct answer is: a basement membrane.

Explanation:

The basement membrane is a thin and fibrous membrane that is found under the epithelium and attaches it to the connective tissue. The basement membrane is composed of two membranes: the basal lamina (with laminin and collagen IV, among other proteins), and the lamina reticularis (that has collagen III making up reticular fibers). The basement membrane also has the function of a mechanical barrier that prevents the invasion of deeper tissues by malignant cells.

Epithelial tissue and connective tissue are two of the four basic tissues found in the body (the other two are nervous tissue and muscle tissue). Epithelial tissue makes up the skin and the inner lining of hollow organs (like the stomach or the trachea), and has multiple functions that are responsible for the function of the organ where it's located. Connective tissue is basically any type of tissue that connects the epithelium to muscle tissue or nervous tissue: from blood, to bone, and to fat.