一将下列的名词变成复数形式
1.book___________________2
duck___________________3
house___________________4
orange___________________5
class___________________6
box___________________7
watch___________________8
bus___________________9
city___________________10
factory___________________11
country___________________12
family___________________13
hero___________________14
potato___________________15
tomato___________________16
photo___________________17
piano___________________18
knife___________________19
leaf___________________20
life___________________21
fish___________________22
sheep___________________23
foot___________________24
tooth___________________25
man___________________26
woman___________________27
fireman___________________28
policeman___________________29
postman___________________30
child__