减速器在使用中常见故障有()
A、连续的噪声
B、不均匀的噪声
C、发热
D、漏油
E、振动
参考答案:A, B, C, D
根据句子意思用适当的词语填空。
1. It’s breakfast ________. Let’s eat eggs and drink milk.
2. I get up at six ________ the morning.
3. They ________ supper at home.
4. —________ dreams, Li Ming!
—Good night, mom!
5. —________ would you like, Jenny?
—Some porridge.
下列有关Na2CO3和NaHCO3性质的比较中,不正确的是( )
A.对热稳定性:Na2CO3 >NaHCO3
B.常温时水溶性:Na2CO3 >NaHCO3
C.与稀盐酸反应的快慢:Na2CO3 >NaHCO3
D.相对分子质量:Na2CO3>NaHCO3