—Are you in Class One?
— .
A:Yes, I'm not
B:No, I am
C:Yes, you are
D:Yes, I am
如图所示,在上海世博会某场馆里,演奏员正用乐器演奏乐曲.编钟发出的音乐声是由于编钟____而产生的;听众能从同一乐曲中分辨出是二胡还是笛子演奏的,主要是因为它们发出声音的____不同.
醇酸树脂是一种成膜性良好的树脂,下面是一种醇酸树脂的合成线路:
— It's one of the things in the world to stay with friends.—I agree. It always makes us relaxed.