造成杂种优势的原因是()。
A.基因的非加性效应
B.上位效应
C.显性效应
D.上述三种都存在
参考答案:A
Dick isn't feeling ______ well this morning because he had ______ food for breakfast. [ ]
A. much too; much too
B. too much; too much
C. much too; too much
D. too much; much too
诊断震颤麻痹最重要的依据是().
A.确切的病史及体征
B.脑脊液检查
C.头部CT
D.头部MRI
E.脑电地形图