用符号和数字表示：
14＋5=____
18＋1=____
19＋1=____
16＋2=____
13＋3=____
如图是一种常用的动圈式话筒。当你对着话筒说话时，声音使与膜片相连的线圈振动，线圈在磁场中的这种振动，能产生随着声音变化而变化的 ____ ，这是 ____ 现象。
– ________ of us think the English examination was difficult.
– But I still don't think ________ could pass it.
