Dear friend,
       I am an American (美国的 ) girl. My name is Alice Green. I am a middle school student. I am fifteen. I have two brothers. They are middle school students, too. We go to school from Monday to Friday. We don't have any classes on Saturdays and Sundays. My father and mother are teachers. They always say China is great. I like reading. I am reading a Chinese book. I think it's very interesting. My brothers and I like playing football and basketball. What sports do you like?
     Let's be good pen pals (笔友), OK? Please write to me soon.
Yours,
Alice Green

小船在200m宽的河中横渡，水流速度为2m/s，船在静水中的航速是4m/s，求：

发芽的土豆只要不吃芽，其余的部分照样吃．

八（1）班某同学学完“中华民族的抗日战争”这一单元后，整理出了知识线索（如图）。促使横线处“蒋介石接受停止内战、联共抗日主张”的关键历史事件是（    ）