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

The roof of the residential building was constructed in August. The waterproof coiled material was paved during the day. It was found that the waterproof coiled material was bulging and leaking during the acceptance after the construction. Explain the causes of the above engineering problems.