城市中的路灯、无轨电车的供电线路等，经常用三角形的结构悬挂．如图是这类结构的一种简化模型，硬杆左端可绕通过B点且垂直于纸面的轴无摩擦的转动，右端O点通过钢索挂于A点，钢索和硬杆所受的重力均可忽略．有一质量不变的重物悬挂于O点，现将钢索缓慢变短，并使钢索的悬挂点A缓慢向下移动，以保证硬杆始终处于水平．则在上述变化过程中，下列说法中正确的是（  ）

力学国际单位制中的三个基本量及基本单位是
①长度——米    ②质量——千克     ③力——牛顿     ④时间——秒

人体内的细胞与外界气体进行气体交换要经过（　　）

    There was a football game on our school football field last week. We played 1 a team from a country school. They didn't come 2 the last minute. They looked worse than we thought. They were wearing 3 clothes and looked like farm boys. We were sure we must be the 4 because we were always the best.

    We found in 5 that they did much better than us after the game began. They 6 their best and they always played as a team. But we didn't. Finally, we 7 the game and we all felt unhappy.

    We thought much 8 the game. We're too proud(骄傲). We're good players, but we can't 9 win. For us, the most important 10 is; One can't judge(判断) a person only by his clothes. We'll never forget the game!