“神七”使用偏二甲肼和四氧化二氮作火箭燃料。偏二甲肼的化学式为C2H8N2,则C2H8N2不含碳碳键的同分异构体有[ ]
A.2种
B.3种
C.5种
D.6种
答案:B
According to scientists, our mental abilities begin to from the age of 27 after reaching the highest level at 22.
A.differ
B.increase
C.develop
D.decline
在对钢管进行喷涂内减阻涂料时,提高喷涂压力,涂膜厚度变化()。