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 ___