🔍 Key Concepts

• Propulsion components on towboats: which parts guide water flow vs. which support the shaft • How a circular structure around the propeller affects thrust and efficiency • Difference between items that surround the propeller vs. those that support or cover it

💭 Think About

• Look at each choice and ask: does this part normally go around the propeller or does it have another primary purpose? • Think about river towboats pushing heavy loads at low speed: which device is commonly used to increase thrust and protect the wheel? • Which term is associated specifically with a ring-shaped housing or duct around a propeller?

✅ Before You Answer

• Make sure the option you pick is known as a ring or duct that encircles the propeller, not just a support or cover. • Verify which term is commonly used on towboats and tugs to improve bollard pull (pulling power). • Eliminate any terms that usually describe a shaft support or a simple cover/hood, not a full circular structure.