I'm afraid I'm not fit for the job, for it is _____ calling for much patience.[ ]

A. it

B. that

C. one

D. which

胰头癌区别于其他壶腹周围癌的常见特点是

A．PTCD显示胆管下端梗阻

B．血管造影提示门静脉受浸润

C．大便潜血(+)，黄疸进行性加重

D．血淀粉酶高于正常

E．大便苏丹染色阳性，显示脂肪颗粒