郑成功之所以被称为中国历史上的民族英雄，是因为他(    

B

    I'm Tom and I like sports. Basketball is my favourite. I play it in. my school in the morning. My school is big and there is a playground and a sports hall in it. Every morning, many teachers and students play sports in the playground. I play there with my friends too. When the weather is bad we play in the sports hall. It's on the left of the playground. Now I'm in the sports hall but I don't play basketball. Some students from London are in our school and I'm their guide (导游).

    My family also like sports too. My parents kick(踢)jianzi near our home every morning. My sister Mary plays table tennis with her classmates in their school. It is small but beautiful.

①平板车的最小长度是多少？

②物块A在平板车上相对于平板车滑行的时间是多少？

图1、图2是由相同的滑轮组装的滑轮组，甲乙两人分别用两装置在相等时间内将质量相等的重物匀速提升相同的高度，空气阻力、摩擦、滑轮和绳子的质量均不计，下列说法正确的是（　　）

2013年5月8日，英国首相卡梅伦在英议会接受质询时表示，英国承认西藏是中国的一部分，不支持“西藏独立”，尊重中国主权。历史上，元朝正式将西藏纳入中国版图管理机构是（　　）