What runs from the pressure reducer/regulator to the demand valve?

• A. the connecting line
• B. the supply hose
• C. the data cable
• D. the exhaust tube

Answer: (A)

Air moves from the pressure reducer/regulator to the demand valve through a line that connects the two parts of the system. This connecting line carries air at the regulator’s intermediate pressure to the second stage, and when you inhale, the demand valve opens to let that air flow into your mouth. Without this line, the demand valve wouldn’t receive air to supply your breaths.

The other options don’t fit this purpose: a data cable isn’t part of the air-delivery path, and an exhaust tube handles the expelled air rather than supplying it. While some might loosely call it a supply hose, the term used here emphasizes the direct link between the regulator and the demand valve—the connecting line.