A client is diagnosed with a herniated lumbar disk at the L-5 interspace. Which of the following symptoms would most likely be the one that first caused the client to seek health care

A．Loss of voluntary muscle control.

B．Loss of bladder control.

C．Back pain that is relieved with resting.

D．Back pain that radiates to the shoulders.

汽车变速器壳体的材料一般选用（）。

A．高碳合金钢

B．低碳合金钢

C．碳素工具钢

D．铸钢