🔍 Key Concepts

• Study where item "O" is located in relation to the impeller and the main flow path through the device. • Think about which component would actually lock or secure a rotating element versus which parts simply guide fluid flow. • Compare the typical function and location of a spindle nut on a rotating shaft with what you see at label "O" in the illustration.

💭 Think About

• Does item "O" appear to be a fastener on the shaft, or a shaped surface that interacts with the fluid moving through the device? • Looking at how fluid would enter and exit this machine, what role would a conical or ring-shaped part at "O" most likely play in controlling or directing that flow? • If the impeller needed to be held tightly to the shaft, where in this cross‑section would you expect the locking or clamping feature to be located?

✅ Before You Answer

• Verify whether "O" is directly threaded onto the shaft or is instead part of a stationary/flow‑shaping structure. • Check if item "O" is in contact with the impeller hub in a way that would lock it, or if it mainly forms a surface along the passage where liquid moves. • Confirm whether any other labeled part, closer to the shaft centerline, looks more like a nut or clamp that would actually secure the impeller or spindle.