写出如图的符合下列条件的角．（图中所有的角均指小于平角的角）．
（1）能用一个大写字母表示的角；
（2）以点A为顶点的角．
解：（1）能用一个大写字母表示的角有∠C，∠B
（2）以点A为顶点的角有∠CAB，∠CAD和∠DAB
一艘轮船从甲港开往乙港，由于顺水，每小时可以航行28千米，3小时到达．这艘轮船从乙港返回甲港时，由于逆水，每小时只能航行21千米．这艘轮船往返一次每小时的平均速度是（ ）
Rules of visiting the Science Museum
Rules
1).First, don't ____ in the museum, or the workers in the museum will ask you to leave.
2). Second, you mustn't take ____ in the museum. But you can take a pen and a notebook to write down some ____ information.
3). Third, follow the guide and don't leave ____ the teachers.
4). Finally, keep the museum clean and tidy while visiting.
Way of contact
Call ____if you have any more questions.
