题目

It is now commonly known that AIDS is a deadly disease. It does great damage to human beings’ immune system, weakening resistance to disease and leading to death due to utter weakness. To this day, there are no existing drugs that can kill AIDS virus. It is a deadly battle between science and AIDS. This is only one side of the story. Although it can not be cured, AIDS is preventable. For those who have not caught the disease, the knowledge of preventive measures seems to be the most powerful weapon at hand. Since the discovery of the first AIDS patient in 1985, the number of HIV carriers is 下图是探究声现象的四种实验情景，下列说法正确的是（ ）A．甲实验说明声音的传播需要介质B．乙实验说明钢尺振动的频率越高，响度越大C．丙实验说明音叉的振幅越大，音调越高D．丁实验说明声波不能传递能量