A

    There were many people on a bus. An old man ____(look) here and there. He wanted to find ____ empty seat. Then he saw one and went to it. A small bag was on the seat. And a young man was beside it.

    "Is this seat empty?" asked the old man.

    "No, it's ____ an old woman. She went to buy some bananas.” said the young man.

    "Well, let me sit here, please. I'll leave here when she ____(come) back, "replied the old man.

    After a few minutes, the bus started. "The old woman ____(not come), but her bag is here. Let me give her the bag. "Then the old man threw the bag out of the bus window.

    The young man jumped up and shouted, "Don't throw! It's my bag!"

北京2008年第29届奥运会火炬接力活动历时130天，传递总里程约13.7万千米．传递总里程用科学记数法表示为（   ）

已知下列方程：
①x-2=$\frac{2}{x}$；②$\frac{x+1}{2}$-1=$\frac{x-3}{3}$③$\frac{x}{2}$=5x-1；④x²-4x=3；⑤x=6；⑥x+2y=0．其中一元一次方程的个数是（　　)

标志中国航天科技步入世界前列水平的是