两药合用，能产生或增强毒性的配伍关系是（）
A.相恶
B.相反
C.相杀
D.相畏
E.相使
参考答案：B
It is the usual ________ in our school that if you spoil any material, you'll have to pay for it. [ ]
A. order
B. argument
C. opinion
D. practice
