纯净物X、Y、Z转化关系如右图所示,下列判断正确的是( )
A:X可能是金属铜
B:Y不可能是氢气
C:Z可能是氯化钠
D:Z可能是三氧化硫
选择适当的词填空:
A. see B. friends C. from D. name E. welcome
Nice to____you again.
We have two new____today!
I'm____Canada.
____back.
My ____ is Tom.
—Is this your English-Chinese dictionary?
—No, it's______