题干

如图所示,用悬挂着的乒乓球接触正在发声的音叉,乒乓球会多次被弹开.这个实验是探究(   )

A:响度是否与振幅有关

B:音调是否与频率有关

C:声音的传播是否需要介质

D:声音产生的原因

上一题 下一题 0.0难度 选择题 更新时间:2019-06-09 01:11:43

答案(点此获取答案解析)

D

同类题2

完型填空

阅读下面短文, 从短文后所给各题的四个选项(A、B、C和D)中, 选出可以填入空白处的最佳选项, 并在答题卡上将该项涂黑。

    Every December the radio station in my city makes a program in which all the poor children can send letters asking for some Christmas presents. One day, as I was 1 the radio, I decided to do something, so I asked four of my friends if they wanted to help a poor child. They2.

    After several days, we learned about a 3from a little child called Juan. In his letter, he 4 some blankets and some clothes and also wanted somebody to help his father5 the house because it was in bad 6.

    We told the radio station that we wanted to 7 Juan. After that, we started to think about how to 8 all the money to buy all that Juan 9. After 5 days, we collected much money and bought many things for Juan. We 10 bought some toys as a little 11for Juan.

    12, on December 22 the radio station gave a party in which all the children who asked for help were 13, and all those helping these children.

    In the party we 14 Juan. We played some games with him and gave him the 15we prepared for him. He was very excited and happy, so were my 16 and I.

    That day was one of the most 17 days in my life, and I learned something 18 from it. Giving help to those in need is one of the most meaningful things that you can do19 this makes you feel good and also makes the persons who you are helping 20. I am going to keep doing that all my life!