I'll never understand how it _____ that he still insisted on going there alone after being told about the

possible danger.    [ ]

A. came about  

B. came across  

C. came out  

D. came up   

男，59岁，肝痛晚期，疼痛剧烈，不能忍受，严重影响日常生活。对其实施镇痛方案，可选用

A．阿司匹林类

B．可待因类

C．弱麻醉性镇痛剂

D．杜冷丁类

E．非麻醉性镇痛剂