A:从液态空气制取氧气
B:水电解生成氢气和氧气
C:冰融化
D:水变成水蒸气
例:
—What are these?
—They are two cups.
如图是某家族遗传系谱图.设甲病显性基因为A,隐性基因为a;乙病显性基因为B,隐性基因为b.据查Ⅰ﹣1体内不含乙病的致病基因.