Answer: B. on the surfaces of organs, on the walls of cavities, on the outer surface of the body, and in glands of the body.
Explanation:
The epithelial tissues are the tissues that are present throughout the parts of the body. They form the covering of the body surfaces. It helps in lining the body cavities and organs. It forms the major tissues of the glands.
These tissues are important as they perform diversity of functions in the body. Such as protection, absorption, secretion, filtration, excretion, sensory reception and diffusion.
Crossing over is the swapping of genetic material that occurs in the germ line. During the formation of egg and sperm cells, also known as meiosis, paired chromosomes from each parent align so that similar DNA sequences from the paired chromosomes cross over one another. Crossing over results in a shuffling of genetic material and is an important cause of the genetic variation seen among offspring.