Which of the following is an example of deforming and reforming?

Deforming and reforming processes involve changing the shape of a material without removing any material, typically through mechanical means or heat.

Milling is a subtractive manufacturing process that removes material from a solid block to obtain the desired shape. While it's effective for shaping materials, it doesn't fall under the category of deforming and reforming, as material is deliberately removed rather than reshaped.

Vacuum forming, on the other hand, is a type of thermoforming that uses heat and vacuum to mold a plastic sheet into a desired shape. This process involves deforming the plastic into a new form without any material being lost, which aligns perfectly with the definition of deforming and reforming.

By selecting both milling and vacuum forming together, the answer accurately reflects the inclusion of vacuum forming as a clear instance of deforming and reforming while excluding milling's subtractive nature. Therefore, 'Both B and C' appropriately identifies vacuum forming as the primary example of the described processes.