已知点P关于x轴的对称点是P₁，点P₁关于原点O的对称点是P₂，点P₂的坐标为（3，4），则点P的坐标是（　　）

人在青春期的最大变化是____器官的发育和成熟。男孩出现____，女孩出现____。青春期的人体变化，还表现在____器官功能的日渐健全，如____收缩力增强、肺____量增大、脑____功能增强等。

    Nowadays more and more Chinese teenagers find life more difficult without their parents. They don't know how ____housework. Because their parents do almost everything for them at home. This is a big problem.

    Joy is 14 years old. One day her parents____away on business(出差), so they asked Joy ____home alone. At first she thought she would be happy ____her parents were not in. She could do what she liked. But it was six o'clock ____the afternoon, she felt hungry.“Oh, it's time ____supper. Where can I get my food?”she said to herself.Later she found some food in the fridge, but she didn't know how to cook.At that moment, she missed her____very much. At last she could only go to the supermarket and____some food to eat.

    Many teenagers are the ____as Joy. So I think they should learn some basic life skills,____as cooking, cleaning their rooms or dressing themselves properly. They shouldn't depend too much on their parents.