下图是某种遗传病的系谱图。3号和4号为正常的异卵孪生兄弟,兄弟俩基因型均为AA的概率是()
A.0
B.1/9
C.1/3
D.1/16
参考答案:B
A number of birdwatchers ______in Zhalong Nature Reserve. The number of them____500.
A.are, are
B.is, is
C.is, are
D.are, is
用柱色谱分离有邻二酚羟基或3-OH或5-OH的黄酮类化合物时,不适合的填充剂是()
A.聚酰胺
B.大孔吸附树脂
C.葡聚糖凝胶
D.硅胶
E.氧化铝