A:汽车鸣笛的声音通常是通过空气传入人耳中的
B:安全带做得较宽,是为了增大压强,保证安全
C:车上配备安全气囊,是为了防止发生撞击时由于惯性对人体造成伤害
D:汽车每过一段时间就需要保养,给有关部件加润滑油,是为了减小部件间的摩擦
Mr. Jackson is a teacher of science in a middle school. His students like his classes because his classes are very interesting. They can learn a lot in his class. The students can make(制作)many things. His little son Val also likes making things. He makes lots of machines(机器), such as a machine like a man. It can do the job that is dangerous(危险的)for people to do. He says, “I want to be a scientist.”根据短文内容,选择正确答案。
如图的两个四边形相似,则∠α的度数是( )
世界上水量最大、流域面积最广的河流是( )