A:打鼓时,放在鼓面上的沙粒不停的跳动,说明发声体在不停的振动
B:放在钟罩内的闹钟正在响,把钟罩内的空气抽出一些后,铃声明显减少,说明声音的传播需要介质
C:贝多芬双耳失聪后,用棍子顶在琴盖上聆听自己演奏的琴声,说明固体能够传声
D:正在发声的音叉接触水面时,水面溅起水花,说明液体能够传声
把新鲜的水草放在养鱼缸里的主要目的是( )
某服装2014年10月底的价格是每件a元,受市场影响,2014年元旦前价格平均下降了10%,到了春节前平均又上升了15%,则春节前的售价是每件( )
Sarah is from France. She lives in Paris. She can speak French and English, but she can't speak Chinese. She has a pen pal in the United States. Her name is Jane and she lives in New York. Sarah's favorite sport is basketball and she can play the guitar, too. Jane's favorite sport is tennis. She can't play the guitar, but she can play the piano and sing.