在下列词中的可数名词前加a或an,不可数名词加/
1.grass 2.milk 3.idea 4.law 5.meat 6.music 7.medicine 8.plant
9.progress 10.programme 11.homework 12.shoe 13.season 14.tennis
15.travel 16.trip 17.water 18.biscuit 19.event 20.eyesight 21.housework 22.postage 23.record 24.sause 25.shampoo 26.steam
27.whale 28.turkey 29.vapour 30.air 31.loaf 32.kindness 33.geography 34.flour