建筑安装工程材料损耗率一般采用( )计算确定。
A.技术测定法 B.比较类推法C.观察法 D.经验估计法
参考答案:C
He _____ play the piano now, but he _____ play it one year ago.[ ]
A. couldn't; can
B. can; couldn't
C. can; could
D. could; can
确诊的伤寒患者,其病原治疗首选下列哪类抗生素
A.睦诺酮类B.氯霉素C.青霉素D.氨基糖苷类E.头孢菌素类