世界上最长的山脉是( )
A:喜马拉雅山脉
B:阿尔卑斯山脉
C:安第斯山脉
D:阿巴拉契亚山脉
在化学方程式CO2+3H2R+H2O中,则R的化学式是( )
____ He's my brother.
____ Who's that boy?
____ Yes, she is.
____ Is she your mother?
____ No, he isn't. He's my teacher.
____ Is he your father?