The ciliated columnar epithelial cells in humans are known to occur in
A. Eustachian tube and stomach lining
B. Bronchioles and Fallopian tube
C. Bile duct and oesophagus
D. Fallopian tube and urethra

Hint: A ciliated epithelium is composed of hair-like cilia and they are mainly columnar. They are located in various places in the body, mainly where filtration is essential. They are most infectious to common cold viruses, such as influenza.

Complete answer: The ciliated epithelium of simple ciliated columnar epithelium is mainly located in the nasal tract, trachea, bronchioles of the respiratory tract, and in the uterus, fallopian tubes of the female reproductive system, and it is also located in the central part of the spinal cord. An interesting fact is that these cells are most infectious to common cold viruses that infect these cells and may kill and as a result of which mucus builds up.
a) Eustachian tube and stomach lining: The eustachian tube is lined by the ciliated columnar epithelium but the stomach lining possesses stratified squamous epithelium.
b) Bronchioles and fallopian tube: These structures possess ciliated columnar epithelium as a result of which, they can propel mucus and egg respectively from these structures.
c) Bile duct and oesophagus: These two layers are covered with stratified squamous epithelium so that food can be pushed forward.
D) Fallopian tube and urethra: The urethra possesses epithelial tissues that are a collagen-rich layer on the outside.
Hence, the correct answer is option B.

Note: The epithelium in the trachea possess cilia that play a major role to filter the air coming to the lungs from the outside. It makes sure that pathogens and dust cannot enter the lung. The epithelium also plays a role in maintaining the moisture and protects the trachea from infections and tissue injury as well as it helps in the facilitation of gases.