下图是一个遗传病的系谱(设该病由一对基因控制,A是显性,a是隐性;图中有阴影的为患者),据图回答:
Ⅱ5和Ⅲ7的基因型分别是()和()
参考答案:Aa;aa
The research mainly deals with the difficulty the students have ________ their attention on their study all
the time.[ ]
A.to focus
B.to be focused
C.focusing
D.focused
釉质发育障碍在1岁以内累及的牙齿为()。
A.
B.
C.
D.
E.