These clothes are _____ sale. [ ]
A. on
B. at
C. of
D. in
答案:A
烯丙吗啡和纳洛酮均属于()
A.非麻醉性镇痛药
B.中枢镇咳药
C.中枢兴奋药
D.麻醉性镇痛药
E.麻醉性镇痛药的拮抗药
请写出钢筋混凝土轨枕的优点?