能保持氧气化学性质的粒子是( )
A:O
B:H2O2
C:O2
D:O2-
I hate it when she calls me at work—I'm always too busy to _____ a conversation with her.
郑和下西洋,最远到达( )
—Yes, I have.
读等高线地形图,回答下列问题: