腰椎间盘突出症患者进行腰椎牵引的初次牵引重量是（）

A.体重的30%

B.体重的40%

C.体重的50%

D.体重的60%

E.体重的80%

A KEY activity for achieving customer satisfaction is to define （）.

A．the business use

B．requirements

C．product specificity

D．change control