Which require surgical treatment about prolapse of lumbar intervertebral disc? A: Bulging and Extrusion B: Extrusion and free fragments in the spinal canal C: Bulging and Schmorl tubercle D: Schmorl tubercle and<br/>free fragments in the spinal canall

3D printing technology can also be called ( ). A: Additive Manufacturing B: removal forming C: extrusion molding D: constrained forming