Which statement best describes the liquefying process as presented?

• A. Cool the oxygen until it liquefies
• B. Mix oxygen with acetylene to form a liquid
• C. Fill a tank with oxygen and pressurize to 2250 psi
• D. Compress oxygen to a high pressure in a tank and continue until 2250 psi is reached

Answer: (D)

The point being tested is how oxygen is stored and prepared in welding contexts: as a compressed gas in a high-pressure cylinder, not as a liquid. The statement that best fits the presented process describes compressing oxygen into a tank and continuing until it reaches the full service pressure, around 2250 psi. This mirrors how cylinders are filled in practice—gas is added and the fill stops when the gauge shows the cylinder is full. The other ideas don’t reflect standard oxygen handling: cooling to liquefy oxygen describes liquid oxygen production, mixing with acetylene to form a liquid isn’t a valid or safe method, and simply claiming to pressurize to 2250 psi without the explicit completion cue misses the typical filling step.