英语难!写出下列名词的单数或复数.1 pencil-boxes2 knives3 sister4 doctor5 fam

1 pencil-boxes pencil-box
2 knives knife
3 sister sisters
4 doctor doctors
5 families family
6 nurse nurses
7 wife wives
8 story stories
9 child children
10 birds bird
11 feet foot
12 mouse mice
13 watch watches
14 classes class
15 bueses 应该是buses吧 bus
16 pears pear
17 postman postmen
18 key keys
19 men man
20 kites kite

1 pencil-box
2 knife
3 sisters
4 doctors
5 family
6 nurses
7 wives
8 stories
9 children
10 bird
11 foot
12 mouses
13 watches
14 class
15 bues