下图是人类的性别决定示意图，甲和乙表示的性染色体分别是
A．X、XY
B．Y、XY
C．Y、XX
D．X、YY
答案：C
Sarah gets a lot of____ from making cakes. And Tony enjoys eating her cakes as well.
A．enjoyment
B．activity
C．collection
D．development
方波积分比相器直接测量两个交流量(_)的时间。
A、极性相同
B、极性相反
