可单独进行动脉主干栓塞的是（）

A．左肾癌

B．子宫肌瘤

C．肠系膜上动脉空肠支破裂出血

D．产后大出血

E．胃大部切除术吻合口出血

____ difficult the work may be, we must go all out to finish it ahead of time.

A．Whatever

B．However

C．How

D．What