吗啡的镇痛作用与其激动脑内阿片受体有关。
参考答案:对
The experiment show that proper amount of exercise, if ________ regularly, can improve our health. [ ]
A. carry out
B. carried out
C. to carry out
D. being carried out
企业向外部物流机构所支付的各项费用是指:()。
A.材料费
B.人工费
C.维护费
D.委托物流成本