---Are you sure you have to do it? It’s been very late.

-----I don’t  know ________I can do it if not now.

A .where           B. why          C. when

(118～120题共用题干)男性，40岁，劳累后突然呕大量咖啡色胃内容物，查体：面色苍白，巩膜轻度黄染，四肢湿冷，脉细数，血压正常。

首选的治疗措施

A．内镜止血

B．静脉点滴止血药物

C．输血

D．应用三腔双囊管