Which feature would be best for making a curved surface in a part?

The "Loft" feature is the most suitable option for creating a curved surface in a part because it allows for the connection of two or more profiles that can be of different shapes, sizes, and orientations. When you create a loft, the software generates a smooth surface that transitions between the selected profiles, which is particularly useful for designing complex, organic shapes that require curvature.

In contrast, while the "Revolve" feature can create curved surfaces by rotating a 2D profile around an axis, it is limited to symmetric shapes. This makes it less versatile for creating non-symmetric or more complex curves.

The "Fillet" feature is primarily used to create rounded edges between two surfaces or edges, which does not create a new surface but modifies existing geometry.

Lastly, the "Extrude" feature extends a 2D shape in one direction to create a 3D object, but it typically results in flat surfaces rather than curved ones. Therefore, when needing to create sophisticated curved surfaces, the lofting process is the preferred method among these options.