_____ people know _____ about it.[      ]

A. Only a little, more    

B. Very few, /    

C. Very little, /    

D. Very a few, more

吗啡喃类合成镇痛药（）.

A．盐酸哌替啶 

B．酒石酸布托啡诺 

C．盐酸美沙酮 

D．盐酸溴己新 

E．磷酸可待因