蝇对人类的危害有()
A.机械性传播疾病
B.幼虫寄生于人体组织器官
C.叮刺吸血
D.传播地方性斑疹伤寒
E.传播睡眠病
参考答案:A, B, C, E
He _____the problem _____in his mind for a whole week before he did anything about it.
A.switched; on
B.kicked; up
C.turned; over
D.took; on
《地表水环境质量标准》基本项目中采用重铬酸钾法分析测定的是()。
A、总氮
B、氨氮
C、化学需氧量
D、生化需氧量