在中国古代，“中央政府的组织，皇权相权是划分的，期间比重纵有不同，但总不能说一切由皇帝专制”。这一状况被彻底改变始于（    ）

如图，一棵大树在一次强台风中折断倒下，未折断树杆AB与地面仍保持垂直的关系，而折断部分AC与未折断树杆AB形成53°的夹角．树杆AB旁有一座与地面垂直的铁塔DE，测得BE=6米，塔高DE=9米．在某一时刻的太阳照射下，未折断树杆AB落在地面的影子FB长为4米，且点F，B，C，E在同一条直线上，点F，A，D也在同一条直线上．求这棵大树没有折断前的高度．（参考数据：sin53°≈0.8，cos53°≈0.6，tan53°≈1.33）

一质量为m的人站在电梯中，电梯加速上升，加速度大小为 $\frac{g}{4}$ ，g为重力加速度．人对电梯底部的压力为（   ）

下列现象中，属于光的直线传播的是（    ）

补全对话

Where       answering        completely     came down    they

A: Hello, I'm Barry Lai, a reporter with TV News. Would you mind ____a few questions about the events of this afternoon?

B: Not at all

A: All right then. ____were you when the birds landed?

B: I was shopping in Central.

A: How many birds do you think there were?

B: I'd say there were about 1,000 birds in all.

A: Can you tell me what ____looked like?

B: They were small brown and green birds.

A: And what did they do, exactly?

B: Well, they ____and landed in Statue Square. They stayed there for about 15 minutes before flying off again.

A: How did people react?

B: Oh, everyone was amazed. Traffic stopped ____and the police had to be called.

A: OK. Thanks very much for talking to me.