确定家禽的育种目标通常要考虑三大因素：（）、（）和（）。
参考答案：市场需求；现有育种群的状况；竞争对手的品性能
阅读短文，回答问题。
Hi! I'm Anna. Nice to meet you. This is my family. Today is Sunday. We are all at home. My mother is
cooking in the kitchen. She is good at cooking. My father is watching a football match. He is a football fan.
He likes playing football very much. My sister and I are playing checkers. My pet dog is sleeping on the floor.
How happy we are!
1. What day is it today?
_________________________________________________________
2. What's Anna's mother doing?
3. Does Anna have a sister?
4. Is Anna's father a basketball fan?
5. What is the dog doing?
下列物质中，是形成酸雨的主要气体的是（ ）
A．N2
B．SO2
C．CO2
D．CO
