After Connecting an Oxygen Regulator to an “H” Cylinder and Turning

After connecting an oxygen regulator to an “H” cylinder and turning the direct-acting valve on, the respiratory therapist attempts to turn on the flow of oxygen. The desired gas flow is not achieved. Which of the following is (are) the most likely problem(s) ?
1. The therapist is using the wrong regulator.
2. The pressure in the cylinder is inadequate.
3. The regulator outlet is obstructed.
4. There is a leak in the connection between the cylinder outlet and the regulator.

A) 1
B) 2 and 4
C) 2 and 3
D) 1, 2, and 4