Many young people like playing football very much. In China we can often see children playing football on the playground. In China and England, people call British soccer football. They don't call it soccer.
    A British soccer ball is round. There are eleven players in a team. But an American football is not round. It's like an egg. They also have eleven players on the field in one team.
    American football is very popular（流行的）in the USA. Players can catch the ball with their hands. But in a British soccer team, only the goalkeeper（守门员）can pick up the ball with his hands.
    Playing ball games is good for you. It can make you happy and healthy.

下列关于基因的描述，正确的是（　　）

①要克服对社会的冷漠情绪和“看客”心理

②必须遵守社会公德，养成良好的文明行为

③国家必须大力加强社会主义道德建设

④要乐于为社会、为他人奉献爱心和力量

有关经纬线的叙述正确的是