several pieces of wood/a piece of wood为什么只能用several pieces of wood,而不用a piece of wood呢?

several pieces of wood/a piece of wood为什么只能用several pieces of wood,而不用a piece of wood呢? the little boy can hum songs and several diffcult ____ 1.musics 2.music 3.pieces of musics4.pieces of music I’ve read _____ sports news about F1 race today.A two B several C a D two pieces of I’ve read _____ sports news about F1 race today.A.two B.several C.a D.two pieces of some pieces of crash、pieces of three pieces of clothes 请问两张纸是pieces of paper还是pieces of papers two pieces of ckae 还是two pieces of cakes pieces of string怎么翻译 pieces of string 怎么翻译 small pieces of earth 是什么意思 pieces of conversision怎么翻译 Bits and pieces of 不理解 Pieces Of My Life 歌词 several millions of several thousands of There are several of