🔍 Key Concepts

• Check valve basic function (what it does for flow direction) • What extra capability the word stop suggests when added to "check valve" • Difference between controlling flow direction and being able to shut off or open flow

💭 Think About

• Ask yourself: what does an ordinary check valve allow or prevent, and in how many directions does fluid normally move through it? • Think about what additional feature a valve needs if you want to use it both as a non‑return valve and as a shutoff or bypass device. • Look at each choice and ask: does this describe an added feature beyond a normal check valve, or just restate what a regular check valve already does?

✅ Before You Answer

• Be clear on what a standard check valve already does (without the word "stop"). • Identify which options describe something new or additional compared to a basic check valve. • Make sure the option you like actually allows the valve to act as both a check valve and some form of manual control.