用吸附柱色谱法分离生物碱常用的吸附剂为
A.纤维素
B.氧化铝
C.硅胶
D.硅藻土
E.聚酰胺
参考答案:B,C
用适当的介词填一填。
1. A postcard has a picture __________ it.
2. Please send the postcard __________ Li Ming __________ Thursday.
3. I have a picture __________ my family.
4. Danny sits down __________ Jenny's left.
高压断路器在运行中当电路发生故障时,与()相互配合,迅速、自动地切断故障电路。
A.保护装置
B.信号装置
C.自动装置
D.保护装置及自动装置