男性，45岁，持续性黄疸伴皮肤瘙痒月余。近来加重。超声见肝内外胆管及胆囊均扩张，扩张的胆总管下端呈截断阻塞，局部隐约见一实性结节。主胰管扩张，内径0.5cm。可能的阻塞病因是

A．壶腹周围癌
B．胆总管结石
C．硬化性胆管炎
D．胆总管囊肿
E．非特性胆管炎症

Quality ______ is the application of planned, systematic quality activities to ensure that the project will employ all processes needed to meet requirements.

A．planning

B．assurance

C．improvement

D．benchmarking