In the respiratory system certain structures allow air to pass from the trachea to the lungs. they are lined with thin muscles and coated with epithelial cells. these structures are called

Although animals share many common characteristics, there is also a great amount of diversity found in animals. which animals are ectothermic, obtain dissolved oxygen in water through gills, have scales, have fins, and live in water?

How can a person  best  reduce the risk of injuries on the road?  

How can mental health issues have an impact on a person’s career?