Answer: D. Its tightly packed cells allow for protection against harmful substances.
Epithelial tissue is a group of epithelial cells. These tissue are found in the external surface of the body. The form the part of external skin, inner lining of the mouth, secretory glands, digestive tract, urogenital tract, lining of the organs like heart, ears, eyes, ventricular system of the brain and central canal of the spinal cord.
The cells that make up the epithelial tissue are tightly packed or are closed bound to one another. The cell layer is thick that only allows certain molecules like air, water to pass through and prevents the entry of the harmful microbes and chemical substances.
