若基因A和a分别控制豌豆的高茎和矮茎这一对相对性状，基因组成均为Aa的亲本杂交，产生的子代性状表现应有( )
A：一种
B：两种
C：三种
D：四种
Lots of university students practice _______ English _______.
The building ________, for which all the villagers collected money, is an animal lab.
