下列山脉中,位于盆地、平原之间,又是第二、三级阶梯分界线的是( )
A:天山山脉
B:昆仑山脉
C:横断山脉
D:巫山山脉
物质的结构决定性质,下列有关说法错误的是( )
— The classroom is ______ clean ______ it was yesterday.— Sorry, I forgot to clean it.
下列关于P2O5的说法中,正确的是( )
The teachers hope all of us hand ________ our homework ________ time every day.