由于受酸侵蚀,而引起牙齿硬组织进行性丧失的酸蚀症的病因有()
A.饮食酸
B.无机酸,如盐酸、硝酸和硫酸等
C.酸性药物
D.胃酸
E.以上均正确
参考答案:E
某氯化镁溶液的密度为d g/cm3,其中镁离子的质量分数为w,a mL该溶液中Cl—的物质的量为:
A.mol
B.mol
C.mol
D.mol
The lazy waiter _______to his boss that he had _______the table.
A.lied; laid
B.lay; laid
C.lied; lay
D.laid; lay