Which of the following is not a type of shaft bearing?

The correct choice identifies a type of bearing that does not fit within the standard classifications of shaft bearings used in engineering systems. Main thrust bearings, line (spring) bearings, and stern tube bearings are all recognized types of bearings that have specific roles in supporting rotating shafts.

Main thrust bearings are designed to handle axial loads and ensure that the rotating shaft can move smoothly without excessive wear or misalignment. Line (spring) bearings provide support while allowing for some axial movement, primarily in applications where shaft alignment might change due to temperature variations or load shifts. Stern tube bearings are utilized in marine applications, specifically to support the propeller shaft in the stern of a ship, providing stability and minimizing friction as the shaft rotates.

In contrast, carbonized bearing is not widely classified within the standard categories of shaft bearings, making it the correct answer for the question. While carbonized bearings might refer to a specific treatment or material characteristic in bearing manufacturing, they do not represent a distinct type of bearing in the same way the others mentioned do. This distinction is important for understanding the various functions and applications of bearings within engineering practices.