在化学实验技能考试中，有一题目是鉴别氢氧化钙溶液和氢氧化钠溶液，某同学进行了如图所示的实验．

阅读下面短文，从短文后各题所给的四个选项（A、B、C和D）中选出最佳选项。

    Look at the car. It is Mr Black's car. It doesn't work now. Mr Black is under it. He is repairing it. Mrs Black is near the car. She is helping Mr Black. A girl is in the car. She is Kate, Mr Black's daughter. Who is the boy in the car? He is Jim, Kate's brother. It is Saturday today. They don't work. They want to go to Zhongshan Park. They all look worried.

下表是“和谐号”列车的部分运行时刻表．

（1）根据表中提供的信息，计算D609次列车从济南至四方全程的平均速度．

（2）全国铁路提速后，乱穿铁路面临的危险将增大．假如某列车正在以上面速度行驶，某同学要想以1.5m/s的速度横穿9m宽的铁路，则他至少应在距列车多少米处横穿铁路才安全．