The pressure of gas in a full cylinder of oxygen is approximately _______ pounds per square inch (psi).

Before a CT scan, the patient should have nothing by mouth ________ hours before the X-ray if contrast media is used.

A. four B. six C. eight D. 10

Which item on the diagram of the cycle of infection is the method by which a pathogen can enter a new host?

A. A B. B C. C D. D E. E